Several beverages and foods rehydrate your body as effectively as water, and some actually keep you hydrated longer. The key is matching what you drink to how dehydrated you are: mild dehydration from a hot day calls for different solutions than dehydration from illness or intense exercise. Here’s what works, why it works, and when to reach for each option.
Why Plain Water Isn’t Always Enough
Water is fine for everyday hydration, but it has a limitation: your body doesn’t hold onto it very well. When you drink plain water on an empty stomach, it dilutes the concentration of your blood, which signals your kidneys to start flushing fluid out. You urinate more, and a good portion of what you drank leaves your body within a couple of hours.
Your small intestine absorbs water fastest when it arrives alongside sodium and a small amount of sugar. A protein called SGLT1 on the lining of your intestinal cells acts like a pump, pulling two sodium ions and one glucose molecule together across the cell wall, and water follows. This is the principle behind oral rehydration solutions used in hospitals worldwide, and it’s also why certain everyday drinks outperform water for hydration.
Milk Is One of the Best Options
Milk consistently ranks as one of the most hydrating beverages available. In a randomized trial that created a “beverage hydration index,” comparing how much fluid people retained two hours after drinking various beverages, skim milk scored 1.58 and full-fat milk scored 1.50, meaning people retained roughly 50% more fluid than they did after drinking the same volume of water. Oral rehydration solutions scored 1.54, putting milk in the same league as medical-grade hydration drinks.
Two things give milk this advantage. First, it naturally contains sodium, potassium, and other electrolytes that slow the rate at which your kidneys dump fluid. Second, milk protein itself plays a significant role. In controlled experiments, milk protein (separated from milk’s electrolytes) accounted for about 56% of milk’s total fluid retention benefit. The protein raises levels of aldosterone, a hormone that tells your kidneys to hold onto sodium and water. It also keeps blood concentration slightly elevated for longer, which delays the signal to urinate. So even if you stripped the electrolytes out of milk, the protein alone would still help you retain more fluid than water.
Oral Rehydration Solutions
If you’re dehydrated from vomiting, diarrhea, or heavy sweating, an oral rehydration solution (ORS) is the gold standard. These drinks are formulated with a precise sodium-to-glucose ratio that maximizes intestinal water absorption. The optimal range is 45 to 60 milliequivalents per liter of sodium and 74 to 111 millimoles per liter of glucose, which translates to a sodium-to-glucose ratio around 0.75 to 0.81.
You can buy premade ORS packets at most pharmacies, or make a simple version at home using the World Health Organization’s recipe: half a teaspoon (3 grams) of salt and 2 tablespoons (30 grams) of sugar dissolved in just over 4 cups (about 1 liter) of clean water. The sugar isn’t there for taste. Without it, the sodium-glucose pump in your intestines can’t activate, and absorption slows dramatically. Getting the ratio right matters: too much sugar pulls water into the gut and can worsen diarrhea, while too little sugar limits absorption.
Sports Drinks: When They Help and When They Don’t
Standard sports drinks contain electrolytes and carbohydrates, but in that beverage hydration index study, they performed no better than water for fluid retention at four hours. That doesn’t mean they’re useless. During prolonged exercise, a sports drink with 1 to 3% carbohydrate concentration actually improves the rate of fluid delivery to your body compared to plain water or carbohydrate-free solutions.
The catch is concentration. Drinks with 8% or more carbohydrate (which includes many fruit juices and some energy drinks) slow stomach emptying and can cause bloating or nausea. If you’re using a sports drink during activity, look for one in the 4 to 6% carbohydrate range, or dilute a concentrated one. Drinks that combine glucose with fructose can handle higher carbohydrate loads without slowing absorption, because the two sugars use different transport pathways in your intestine.
Coconut Water
Coconut water is naturally rich in potassium, containing about 142 milligrams per 100 milliliters, which is considerably more than most sports drinks. It’s a reasonable option for mild dehydration and tastes pleasant enough that people tend to drink more of it. However, it’s relatively low in sodium (about 45 milligrams per 100 milliliters), which is the electrolyte most critical for fluid retention. If you’re rehydrating after heavy sweating, adding a small pinch of salt to coconut water improves its effectiveness.
Coffee, Tea, and Other Caffeinated Drinks
The idea that coffee and tea dehydrate you is outdated. In a crossover study where regular coffee drinkers consumed four cups per day (averaging about 308 milligrams of caffeine), researchers found no difference in hydration status compared to drinking an equivalent amount of water, measured across blood and urine markers. Tea, iced tea, cola, and diet cola all produced the same cumulative urine output as water over four hours in the beverage hydration index trial.
Caffeine does have a mild diuretic effect, but only at doses above roughly 500 milligrams, which is about five or six cups of coffee consumed in a short window. Below that threshold, the fluid in your coffee or tea more than compensates for any extra urine production. If you’re a habitual caffeine drinker, your body adapts further, blunting the diuretic response. So your morning coffee counts toward your daily fluid intake.
Foods That Contribute to Hydration
About 20% of most people’s daily water intake comes from food rather than drinks, and choosing water-rich foods can meaningfully boost hydration. The top performers are:
- Cucumbers: over 96% water
- Iceberg lettuce: 96% water
- Celery: about 95% water
- Tomatoes: about 95% water
- Zucchini: almost 95% water
Watermelon, strawberries, and cantaloupe are similarly water-dense. These foods have an advantage over drinking plain water because they contain natural sugars, minerals, and fiber that slow digestion and allow your body to absorb the fluid gradually rather than processing it all at once. A salad with cucumber, tomato, and lettuce alongside a glass of water is a more effective hydration strategy than the glass of water alone.
How to Tell If You’re Actually Dehydrated
Your urine color is the simplest way to gauge your hydration. Pale straw or light yellow means you’re well hydrated. Dark yellow or amber signals that you need more fluid. Researchers have validated this approach against lab measurements: urine that’s clearly dark correlates with a specific gravity of 1.020 or higher, which is the clinical threshold for dehydration. If your urine is consistently pale (nearly clear), you may actually be overhydrating, which dilutes electrolytes and offers no benefit.
Other reliable signs of mild to moderate dehydration include a dry or sticky mouth, fatigue that comes on faster than expected, and a headache that develops gradually over the day. Thirst itself is a late signal. By the time you feel genuinely thirsty, your body has already lost 1 to 2% of its water, enough to affect concentration and physical performance. Sipping consistently throughout the day, rather than chugging a large amount at once, keeps your hydration steadier because your intestines can only absorb fluid at a limited rate.
Matching the Drink to the Situation
For everyday hydration when you simply want variety beyond water, milk, tea, coffee, and water-rich fruits and vegetables all contribute meaningfully. For exercise lasting under an hour, water is typically sufficient. For exercise lasting longer than an hour, or in intense heat, a sports drink with a low to moderate carbohydrate concentration (1 to 6%) and added sodium helps replace what you lose in sweat. For dehydration caused by illness, particularly vomiting or diarrhea, an oral rehydration solution with the right salt-to-sugar balance is the most effective option and can be made at home in minutes.