For most workouts, water is all you need. If your session lasts longer than 90 minutes or involves heavy sweating, a drink with electrolytes and carbohydrates becomes genuinely useful. The key is matching what you drink to how long and how hard you’re working, and getting the volume right: aim for 4 to 8 ounces every 15 to 20 minutes during exercise.
Water Covers Most Workouts
If you’re exercising for less than 90 minutes at a moderate intensity, plain water replaces everything you’re losing. Your body stores enough carbohydrates and electrolytes to fuel a typical gym session, run, or fitness class without any special drink. The priority is simply keeping up with fluid losses so your performance doesn’t drop and you don’t overheat.
How much water depends on the conditions. During moderate activity in mild weather, 4 ounces every 20 minutes is enough. For high-intensity exercise in the heat, you may need closer to 8 ounces every 15 minutes. That works out to roughly 16 to 32 ounces per hour, which is a wide range for a reason: sweat rates vary enormously from person to person.
When a Sports Drink Actually Helps
Once you cross the 90-minute mark, your stored carbohydrates start running low and your cumulative electrolyte losses become significant enough to affect performance. This is where a carbohydrate-electrolyte drink earns its place. It does two things water can’t: it feeds your working muscles a usable fuel source and replaces the sodium you’re sweating out.
The carbohydrate concentration matters. A 6% solution (roughly what most commercial sports drinks contain) delivers more total fuel and solute absorption than a diluted 3% version, without slowing down how quickly the fluid leaves your stomach. If you’re diluting a sports drink with extra water thinking it will absorb faster, you’re mostly just reducing the energy it provides.
Situations where a sports drink makes a clear difference:
- Endurance sessions over 90 minutes (long runs, bike rides, hikes)
- High-intensity training in heat, where sweat rates spike
- Back-to-back sessions with limited recovery time between them
- Heavy sweaters who notice salt residue on their clothes or skin
For a 45-minute weight training session or a casual jog, a sports drink won’t hurt, but it’s adding calories you probably don’t need. Water does the job.
Sodium: The Electrolyte That Matters Most
Sweat isn’t just water. The average sodium concentration in sweat is roughly 1,000 to 1,500 milligrams per liter, and that number is higher if you’re not acclimatized to hot conditions. Over a long, sweaty workout, those losses add up fast. Workers exercising in heat can lose 5 to 6 grams of sodium over a full shift, equivalent to 10 to 15 grams of table salt.
For recreational exercisers doing shorter sessions, these losses are manageable and easily replaced by your next meal. But during prolonged endurance exercise, actively replacing sodium mid-workout helps maintain fluid balance and prevents your blood sodium levels from dropping too low. Most sports drinks contain some sodium, though the amount varies. If you’re a particularly heavy or salty sweater, electrolyte tablets or packets that you add to water let you control the dose more precisely.
The Risk of Drinking Too Much
Overhydrating during exercise is a real and sometimes serious problem called exercise-associated hyponatremia. It happens when you drink so much fluid that it dilutes the sodium in your blood. Mild cases cause lightheadedness, nausea, headache, and fatigue. Severe cases can lead to confusion, seizures, and collapse.
The biggest risk factors are drinking more than about 1.5 liters per hour (well beyond what most people actually need), exercising in high heat for more than two hours, and consuming only plain water during very long events. Forcing yourself to drink on a rigid schedule regardless of thirst is how most people get into trouble. Drinking to thirst is a safer strategy than trying to stay ahead of it by chugging fluids constantly.
Caffeine During Exercise
Caffeine consistently improves endurance performance at doses of 3 to 6 milligrams per kilogram of body weight. For a 150-pound person, that’s roughly 200 to 400 milligrams. Most people take caffeine before a workout, but there’s evidence that consuming it during exercise, particularly in the later stages of a long event, can be just as effective. Even a low dose taken late in a race (like flat cola in the final miles) has shown comparable benefits to a larger dose taken an hour beforehand.
If you’re considering caffeinated drinks or gels mid-workout, this works best for sessions lasting over an hour where fatigue is the limiting factor. For a standard gym workout, your pre-workout coffee is already doing the job.
How to Figure Out Your Sweat Rate
The most practical way to personalize your hydration is to calculate your sweat rate. Weigh yourself without clothes before and after a workout, then account for any fluid you drank during the session. Every gram of weight lost equals roughly one milliliter of sweat. Divide total sweat loss by the number of minutes you exercised, and you have your sweat rate in milliliters per minute.
For example, if you lost 1 pound (454 grams) during a 60-minute run and drank 16 ounces (480 mL) during that run, your total sweat loss was about 934 mL, or just under a liter per hour. Your goal during future sessions would be to replace most of that, not necessarily all of it. A small amount of body weight loss (up to about 2%) during exercise is normal and not harmful.
Do this test a few times in different conditions, because your sweat rate in July will look very different from your sweat rate in January.
Checking Hydration Before You Start
What you drink during a workout matters less if you start dehydrated. A quick check: your urine should be a pale yellow, roughly the color of lemonade. If it’s dark or concentrated, drink 16 to 20 ounces of water in the two hours before you exercise to give your body time to absorb it.
After your workout, replacing lost fluids continues to matter. A good target is 16 to 24 ounces of fluid for every pound of body weight you lost during the session. Including some sodium in that post-workout fluid, whether from a drink or from food, helps your body retain the water rather than just sending it straight through to your bladder.