With the weather heating up, we all should be reaching for hydrating fluids more frequently. Tradition tells us that we should only drink water. After all, it's zero calorie, safe, and basically free (if you pay for your utilities, that is). Sports drinks, which can be highly caloric and filled with sugar, are really only necessary for athletes and people doing a lot of sweating (i.e., not people who are just out strolling the neighborhood). But what about soda?

Water cooler advice tells us soda is off-limits because it's dehydrating. The logic goes that soda, with its caffeine and sugar, doesn't replace any of the fluids you're losing while you sweat. The caffeine, which can be a diuretic, will actually make you need to urinate more quickly, and you'll lose more fluid. The myth implies that drinking soda is actually worse than not drinking anything at all. So what's the truth?

Soda isn't dehydrating. "When it comes to caffeine, there’s a lot of misinformation about the diuretic impact of the drug. If you drink two liters of soda, you’ll hold on to most of it, but not as much as you would if you drank two liters of water,” says Dr. Douglas Casa, a kinesiology professor at the University of Connecticut and chief operating officer at the school's Korey Stringer Institute.

In other words, you’re still hydrating yourself. “You don’t have a net deficit. You just don’t retain quite as much fluid as you would if you drank something that doesn’t have caffeine," Casa says.

So should you start reaching for the bubbly when you're thirsty? Well, no. Water, low- or no-calorie drinks, teas, even iced coffees with no sweetener or milk are much preferred over soda. But if soda is all you have and you feel yourself getting really thirsty, go ahead and have some. Hydrating yourself, when you're starting to feel the effects of dehydration, is most important. Just switch to water as soon as you can.

“It is so easy to get to 1 to 2 percent dehydration. We’re busy, we don’t have water with us, and we’re rushing around. That type of dehydration is very mild, almost imperceptible when it comes to feeling thirsty, but the things people would want functioning well for their general living—cognitive function, mood, and vigor—are negatively influenced by that very small amount of dehydration,” Casa says.