Drink Mix, Gels, or Both: How to Build Your Race-Day Fuel Stack

The fuel format question nobody asked five years ago

Five years ago, race fueling was simple. You carried gels, you took one every 45 minutes, and you washed it down with water from the aid station. If you were fancy, you might carry some chews as backup.

That playbook is dead.

High-carb drink mixes like Maurten 320, Neversecond C90, and Flow Formulas have rewritten race nutrition. Instead of cramming down a sticky gel every half hour, you can sip 80-90 grams of carbohydrate per hour through your bottles. Ironman has switched its entire on-course nutrition to Maurten globally, decoupling hydration from fueling for the first time in the sport's history.

But here's the problem: drink mix isn't automatically better than gels. And gels aren't automatically better than drink mix. The right answer depends on your body, your race, and your targets.

This is how to figure out which fuel format — or combination — actually works for you.

What each fuel format does well

Every fuel format solves a different problem. Understanding the trade-offs is the first step to building a stack that works.

Drink mix

High-carb drink mixes dissolve carbohydrate directly into your bottles, combining hydration and fueling into a single action. A 500ml bottle of Maurten 320 delivers 80g of carbs. Neversecond C90 delivers 90g per serving.

When drink mix wins:

• You want to reduce the number of things you need to manage mid-race
• You struggle to stomach gels but can tolerate sipping
• You're doing a bike leg (triathlon, cycling) where bottles are easy to access
• You want steady-state fueling with no spikes

The catch: When your drink mix carries your carbs, you lose the ability to separate hydration from fueling. On a hot day, you might need more fluid but not more carbs. If you drink more to cool down, you overshoot your carb target and risk GI distress. If you hold back to avoid excess carbs, you dehydrate.

Gels

A standard gel delivers 20-30g of carbs in a concentrated packet. You take it with water from an aid station or your own bottle.

When gels win:

• You need precise control over carb timing (take exactly 25g every 20 minutes)
• You're running and can't easily carry bottles
• Conditions are hot and you need to drink for hydration independently of fueling
• You want the flexibility to increase or decrease fuel without affecting fluid intake

The catch: Gels require water to digest properly. If aid stations are far apart or you can't carry enough plain water, gels without adequate fluid can sit in your stomach and cause nausea. They also create a spike-and-dip pattern of carb delivery rather than the steady stream a drink mix provides.

Chews and solid food

Chews (like Clif Bloks or Skratch chews) and solid food (rice cakes, dates, PB&J) deliver carbs in a slower-digesting format. They're common in ultra events and on the bike.

When solid food wins:

• Events longer than 4-5 hours where you need variety and palatability
• You experience "flavour fatigue" from sweet gels and drink mixes
• Early stages of a long event when intensity is low and digestion is easier

The catch: As intensity increases, blood flow shifts away from your gut and toward your working muscles. Solid food becomes harder to digest. Most athletes need to transition to gels or drink mix for the final third of a race.

The variable most people ignore: your sweat rate

Here's where fuel format advice usually goes wrong. Every article compares products in isolation. But the right format depends on a number that's unique to you: how much fluid you need per hour.

If you're a light sweater (400-600ml per hour), a single bottle of high-carb drink mix might deliver both your fluid and carb needs simultaneously. That's efficient. One action, two problems solved.

If you're a heavy sweater (1,000-1,200ml per hour), you need far more fluid than a single bottle of drink mix can deliver. Drinking enough Maurten 320 to stay hydrated would mean consuming 160g+ of carbs per hour — far beyond what any gut can absorb. You'd be doubled over before the halfway point.

Heavy sweaters almost always need to separate hydration and fueling. That means plain water or electrolyte drink for hydration, plus gels or a lower-concentration drink mix for carbs. Light sweaters can often consolidate.

This is exactly why a personalised fueling plan matters more than any product review. Your sweat rate dictates the format before your taste preference does.

How to build your fuel stack: a decision framework

Step 1: Know your per-hour carb target

Before choosing a format, you need to know how many grams of carbohydrate per hour your body needs. This depends on your body weight, pace, and event duration.

General targets:

• Half marathon (sub-2 hours): 30-60g per hour
• Marathon (3-4 hours): 60-90g per hour
• Marathon (4-5+ hours): 60-80g per hour (lower intensity, longer duration)
• Ironman bike: 80-120g per hour
• Ultra events (50k+): 60-90g per hour (with real food mixed in)

These are ranges, not prescriptions. Your actual number depends on your gut tolerance, which you build through training.

Step 2: Know your fluid target

Estimate your sweat rate by weighing yourself before and after a training run of at least 60 minutes. The formula:

Sweat rate (ml/hr) = (pre-weight in grams - post-weight in grams + fluid consumed in ml) / hours of exercise

Once you know your hourly fluid need, you can calculate how much of that fluid can carry carbs versus how much needs to be plain water or electrolyte drink.

Step 3: Match format to the math

If your carb target is 60g/hr and your fluid target is 500ml/hr: A single bottle of high-carb drink mix (60-80g per 500ml) handles both. You may not need gels at all. Simple, efficient.

If your carb target is 80g/hr and your fluid target is 900ml/hr: One bottle of drink mix (80g carbs in 500ml) plus 400ml of plain water or electrolyte drink. No gels needed, but you're carrying two different bottles or relying on aid station water.

If your carb target is 90g/hr and your fluid target is 1,000ml/hr: This is where the hybrid approach works best. A moderate-carb drink mix (40g per 500ml) in one bottle, plus 500ml of electrolyte drink, plus one gel (25g) every 30-40 minutes. Three sources, full coverage, full flexibility.

If you're running a marathon and can't carry bottles: Gels are your primary fuel source. Take one every 20-30 minutes (depending on your target), wash down with water at aid stations. Consider carrying a small soft flask of electrolyte drink for sodium between stations.

Step 4: Choose your carb sources wisely

Not all carbs absorb at the same rate. Your gut has two transport pathways:

• SGLT1 transporter (glucose, maltodextrin): maxes out at roughly 60g per hour
• GLUT5 transporter (fructose): adds another 30-40g per hour on top

To absorb more than 60g per hour without GI distress, you need a product that uses both pathways — typically a 2:1 or 1:0.8 ratio of glucose (or maltodextrin) to fructose. Most modern high-carb products (Maurten, Neversecond, SiS Beta Fuel) use this dual-source approach. Check the label before building your stack.

If you're mixing formats — say, a maltodextrin-based drink mix plus a fructose-heavy gel — you're accidentally creating your own dual-source blend. That can work, but only if you track the ratios.

Step 5: Train with your stack, not just your legs

Gut training is real. Research shows that athletes who practise their race nutrition at target carb rates during training tolerate significantly more carbohydrate on race day. Your gut adapts — intestinal transporters upregulate, gastric emptying speeds up, and GI symptoms decrease.

The protocol:

• Start at 40-50g of carbs per hour on long runs
• Increase by 10g per hour every 2-3 weeks
• Practise with the exact products and formats you'll use on race day
• Do at least 4-6 long runs at your target race-day carb rate before the event

If a format causes problems in training, it will cause worse problems on race day. Find out now.

The hybrid stack: why most experienced athletes mix formats

Talk to athletes who have dialled in their nutrition over years of racing, and most of them don't use a single format. They use a combination — what we call a "hybrid stack."

A typical hybrid stack for a 4-hour marathon targeting 75g carbs per hour:

| Time | Source | Carbs | Notes | |------|--------|-------|-------| | Start | 500ml drink mix | 40g | Sip over first hour | | 0:25 | Gel | 25g | Take with water at aid station | | 0:50 | Gel | 25g | Take with water | | 1:00 | Refill bottle at aid station | — | Plain water or electrolyte | | 1:15 | Gel | 25g | Continue every 25 min | | ... | Alternate gels + water | 25g each | Adjust if stomach allows |

The hybrid approach gives you levers to pull mid-race. Feeling queasy? Skip the next gel and rely on drink mix for a bit. Running hot? Drink more plain water without overshooting carbs. Feeling strong? Add an extra gel.

Rigid single-format plans break when conditions change. And conditions always change.

Hot weather changes everything

Summer heat is the single biggest reason fueling plans fail. When core temperature rises, blood diverts from your gut to your skin for cooling. Your gut's ability to absorb carbs drops, while your fluid needs spike.

In heat above 25C (77F):

• Your sweat rate may increase 30-50% compared to cool conditions
• Your gut absorbs carbs more slowly
• Concentrated drink mixes become harder to tolerate
• GI distress risk spikes when carb concentration in your stomach is too high

The adjustment: dilute your drink mix (use more water per serving), shift more carbs to gels spaced further apart, increase plain water intake, and add 200-500mg of sodium per hour beyond your cool-weather baseline.

If your spring fueling plan worked perfectly at 15C and you haven't adjusted for 30C, the plan is going to fail. Not because the products changed — because your body did.

Where Sweatr fits in

Building a fuel stack requires knowing three personal numbers: your carb target per hour, your sweat rate, and your sodium loss rate. Those numbers change with fitness, heat, humidity, and training load.

Sweatr calculates all three from your Apple Watch, Garmin, and Strava data — no sweat patches, no lab tests, no guesswork. It builds your personalised fueling plan, maps it to real products you can buy, and adjusts it as conditions change.

Instead of guessing which fuel format fits your body, you get a plan built from your actual data. That's the difference between a strategy and a hope.

The bottom line

There is no universally best fuel format. Drink mix is not better than gels. Gels are not better than drink mix. The right answer is the format — or combination of formats — that lets you hit your personal carb and fluid targets without your stomach shutting down.

Know your numbers. Match your formats to the math. Train your gut with your exact race-day stack. And when race day arrives, you'll know exactly what to carry, when to take it, and how to adjust when the plan meets reality.