Alcohol is the biggest dehydration culprit in your glass, but it’s not the only one. Sugary sodas, energy drinks, and even coffee in large amounts can tip your fluid balance in the wrong direction. The key isn’t always avoiding these drinks entirely. It’s understanding how much of each actually starts working against you.
Alcohol: The Strongest Dehydrating Drink
Alcohol causes more fluid loss than any other common beverage. It works by suppressing your body’s main water-retention hormone, vasopressin (sometimes called antidiuretic hormone). Normally, vasopressin signals your kidneys to reabsorb water and send it back into your bloodstream. Ethanol disrupts this process at the nerve level, blocking the calcium signals that trigger vasopressin’s release. With less vasopressin circulating, your kidneys let far more water pass straight into your bladder.
This is why you urinate so frequently when drinking beer, wine, or cocktails. You’re not just passing the liquid you consumed. You’re losing additional water your body would have otherwise retained. The stronger the drink, the more pronounced the effect. A glass of wine with dinner has a milder impact than several shots of liquor, partly because lower-alcohol beverages contribute more water relative to the ethanol they contain.
The dehydrating effect of alcohol also compounds over time during a drinking session. As your blood alcohol level rises, vasopressin suppression increases, and each subsequent drink pushes you further into a fluid deficit. This is a major reason hangovers involve headaches, dry mouth, and fatigue: by morning, your body has lost significantly more water than it took in.
Coffee and Tea: Less Dehydrating Than You Think
Caffeine is a mild diuretic, meaning it increases urine production. But the threshold where this becomes meaningful is higher than most people assume. Research has suggested that caffeine doses above 300 milligrams may trigger an acute increase in urine output. A standard 8-ounce cup of brewed coffee contains about 96 milligrams of caffeine, so you’d need roughly three cups in a short window to approach that level. A single espresso shot has about 63 milligrams.
Here’s the important part: a meta-analysis published in the Journal of Science and Medicine in Sport found that even at the 300-milligram mark, caffeine dosage alone didn’t reliably trigger a significant diuretic effect across studies. The water in coffee and tea largely offsets whatever extra urine caffeine produces. For most people drinking one to three cups a day, coffee and tea contribute to hydration rather than undermining it.
Regular caffeine drinkers also develop a tolerance to its diuretic properties. If you have coffee every morning, your body adapts and produces less extra urine in response than someone who rarely consumes caffeine. So your daily cup or two is essentially hydrating you like water with a mild asterisk.
Sugary Drinks and Osmotic Effects
Heavily sweetened beverages can work against hydration through a process called osmotic diuresis. When a high concentration of sugar enters your bloodstream and eventually reaches your kidneys, the sugar molecules pull extra water into the urine through osmosis. Your kidneys can’t reabsorb the excess sugar efficiently, and water follows it out. The result is increased urination that drains more fluid than the drink provided.
This effect is most pronounced with drinks that have very high sugar concentrations, like undiluted fruit juice, full-sugar sodas consumed in large quantities, and sweetened iced teas. A single can of regular soda is unlikely to dehydrate a healthy person on its own, but drinking several throughout the day without also drinking water can gradually shift your fluid balance in the wrong direction. The sugar also slows gastric emptying, which means the water in the drink takes longer to reach your cells.
For people with elevated blood sugar, whether from diabetes or simply from consuming large amounts of sugar at once, this osmotic effect becomes much more significant. High blood glucose is one of the recognized causes of osmotic diuresis, which is why increased thirst and frequent urination are classic early signs of uncontrolled diabetes.
Energy Drinks: A Double Problem
Energy drinks combine two dehydrating forces in one can. Most contain both high-dose caffeine and substantial sugar. As Columbia University Irving Medical Center explains it, sugar molecules pull water out of the body while caffeine increases urination, and together they double up to accelerate dehydration.
A typical 16-ounce energy drink can contain 150 to 300 milligrams of caffeine, enough to approach or exceed the diuretic threshold in a single serving. Pair that with 50 to 60 grams of sugar, and you have a drink that works against your fluid balance from two directions simultaneously. Sugar-free versions eliminate the osmotic component but still deliver a large caffeine dose.
The risk increases when people use energy drinks during exercise or in hot weather, situations where the body is already losing fluid through sweat. Relying on an energy drink as your primary fluid source during physical activity can leave you more dehydrated than when you started.
Drinks With Minimal Dehydration Risk
Not every flavored or caffeinated drink is a problem. Most teas contain 25 to 50 milligrams of caffeine per cup, well below the threshold for meaningful diuretic effects. Diet sodas, while caffeinated, typically contain only about 33 milligrams per 8-ounce serving for cola varieties. Many citrus-flavored sodas and root beers contain no caffeine at all.
Milk, coconut water, and diluted sports drinks all hydrate effectively. Water remains the gold standard, but you don’t need to drink exclusively water to stay hydrated. The key is balancing any dehydrating beverages with enough plain fluids to compensate.
How to Tell If Your Drinks Are Dehydrating You
Urine color is the most practical self-check. Researchers use an eight-point color scale ranging from 1 (pale yellow) to 8 (dark greenish brown) that correlates strongly with actual hydration measurements. Pale straw or light yellow (values 1 through 3) indicates good hydration. Dark yellow or amber (values 5 and above) signals you need more fluids. In studies, significant whole-body dehydration of about 5% of body mass pushed urine color from a 1 all the way to a 7 on that scale.
Other early signs include dry lips, mild headache, feeling thirsty (which already means you’re slightly behind on fluids), and reduced concentration. If you notice these symptoms after a night of drinking or a day fueled mostly by energy drinks and soda, water is the simplest fix. Drinking a glass of water between alcoholic beverages, or alternating sugary drinks with plain water throughout the day, can prevent most beverage-related dehydration before it starts.