Summer cocktails are a staple of pool days, beach vacations, brunches, and warm nights out. But while that refreshing drink may help you cool down, some popular cocktails can contribute to dehydration, especially when you’re already spending time in the heat.
A new August 2026 analysis from wellness experts at Instant Hydration compared more than 30 popular summer cocktails based on their estimated pure alcohol, sugar, and caffeine content to determine which drinks may have the biggest impact on hydration.
According to the study, the Vesper ranked as the most dehydrating cocktail, while lower-alcohol drinks such as the Aperol Spritz and Hugo Spritz landed toward the other end of the list.
Here’s a look at the cocktails that stood out.
1. Vesper
Pure alcohol: 49.8 mL
Estimated sugar: 1.33 grams
Practical water pairing: 1,000 mL
The Vesper took the top spot for dehydration in the study, largely because it contained the highest amount of pure alcohol among the cocktails analyzed.
With nearly 50 mL of pure alcohol in a serving, the study estimates that drinkers should pair it with about 1 liter of water.
2. French 75
Pure alcohol: 42.1 mL
Estimated sugar: 6.42 grams
Practical water pairing: 850 mL
The French 75 might seem like a light and bubbly summer choice, but it ranked second in the analysis.
A standard serving contains an estimated 42.1 mL of pure alcohol, along with 6.42 grams of sugar.
3. Margarita
Pure alcohol: 35.5 mL
Estimated sugar: 7.21 grams
Practical water pairing: 700 mL
It’s hard to imagine summer without a Margarita, but the classic cocktail ranked third among the most dehydrating drinks in the study.
The analysis found approximately 35.5 mL of pure alcohol and 7.21 grams of sugar in a standard serving.
4. Manhattan
Pure alcohol: 31.9 mL
Estimated sugar: 4.61 grams
Practical water pairing: 650 mL
The Manhattan may be a smaller cocktail, but its concentrated combination of whiskey and vermouth gives it a relatively high alcohol content.
The study estimates that roughly one-third of the drink’s pre-dilution volume is pure alcohol.
5. Spicy Margarita
Pure alcohol: 32 mL
Estimated sugar: 7.14 grams
Practical water pairing: 650 mL
The Spicy Margarita follows closely behind the classic version.
The analyzed recipe contains tequila and Cointreau in a relatively small serving, resulting in an estimated 32 mL of pure alcohol.
6. Old-Fashioned
Pure alcohol: 27.6 mL
Estimated sugar: 4.19 grams
Practical water pairing: 550 mL
Another cocktail known for packing plenty of alcohol into a relatively small serving, the Old-Fashioned also made the study’s list of drinks with a greater potential impact on hydration.
7. Passion-Fruit Margarita
Pure alcohol: 28.6 mL
Estimated sugar: 5.99 grams
Practical water pairing: 550 mL
The tropical twist on the classic Margarita combines a significant amount of alcohol with nearly 6 grams of estimated sugar per serving.
The study estimates that about 550 mL of water would be needed as a practical pairing.
8. Mai Tai
Pure alcohol: 30 mL
Estimated sugar: 22.41 grams
Practical water pairing: 600 mL
The Mai Tai stands out for a different reason: it’s the sweetest cocktail on the list.
The study estimates that a serving contains 22.41 grams of sugar, significantly more than the other cocktails highlighted in the analysis.
Despite having less pure alcohol than some of the cocktails above it, its combination of alcohol and sugar earned it a spot among the drinks with a higher dehydration impact.
9. Dirty Martini
Pure alcohol: 24.8 mL
Estimated sugar: 0.22 grams
Practical water pairing: 500 mL
The Dirty Martini has very little sugar compared with most of the cocktails on the list, with an estimated 0.22 grams per serving.
However, its relatively high alcohol content still puts it among the more dehydrating cocktails analyzed.
10. Rosita
Pure alcohol: 26.3 mL
Estimated sugar: 6.88 grams
Practical water pairing: 550 mL
Rounding out the top 10 is the Rosita, which contains an estimated 26.3 mL of pure alcohol and 6.88 grams of sugar per serving.
The study’s practical water pairing for the cocktail is approximately 550 mL.
What About Aperol Spritz and Hugo Spritz?
Surprisingly, not every summer cocktail ranked highly for dehydration.
The study found that Aperol Spritz and Hugo Spritz were among the least dehydrating cocktails analyzed, with both containing less than 13 mL of pure alcohol per serving.
Of course, that doesn’t mean either drink is a substitute for water. Alcohol can contribute to fluid loss, and factors such as heat, exercise, and how much alcohol you consume can also affect hydration.
What About the Espresso Martini?
The Espresso Martini may seem like an obvious candidate for the list because it combines alcohol with caffeine.
The study estimates that an Espresso Martini contains approximately 110 mg of caffeine, but it didn’t make the top 10 most dehydrating cocktails.
Instead, cocktails with higher amounts of alcohol and/or sugar ranked ahead of it in the analysis.
Why Alcohol Can Affect Hydration
Alcohol can contribute to dehydration because it interferes with the body’s ability to retain water. It can increase urination, meaning you may lose more fluid while drinking.
That effect can become particularly important during the summer. Spending hours in the sun, swimming, exercising, or simply being outside in high temperatures can increase fluid loss through sweating.
That’s why experts recommend paying attention to hydration when drinking alcohol, particularly during hot-weather activities.
An expert from Instant Hydration noted that cocktails can feel refreshing even when their effects on hydration may be the opposite, particularly when they’re combined with activities such as sunbathing, swimming, and spending long nights outdoors.
The Sweetest Summer Cocktail
If you’re more concerned about sugar than alcohol, the Mai Tai was the clear standout.
With an estimated 22.4 grams of sugar per serving, it was the sweetest drink in the study.
For comparison, the Vesper contained just 1.33 grams, while the Manhattan contained approximately 4.61 grams.
The Bottom Line
You don’t necessarily have to skip your favorite summer cocktail. Instead, consider making water part of your plans. Try alternating alcoholic drinks with water, drinking water before heading out for the day, and paying particular attention to hydration when you’re spending extended periods in the heat.
Also, keep in mind the study’s “practical water pairing” is an estimate from Instant Hydration’s methodology, not a medically established amount of water required to literally “cancel out” a cocktail’s effects.
When you’re sitting by the pool, don’t forget the most important summer beverage of all: water.
