Your body is 60 percent water, and you can't live without it for very long. You excrete (eks-KREET) at least a quart of water every day, so you must drink at least that much to avoid becoming dehydrated. A good rule is to drink more than what you think you'll need.Nearly all foods contain water, and some are 90 percent fluid. It's important to keep your body well hydrated, especially if you work out, are in the hot sun, or are very physically active. When you sweat a lot, you lose salt and potassium. If you exercise longer than one hour, you may need a sports drink to replenish those important electrolytes (uh-LEC-tro-lights). But generally water is superior to sports drinks, because many commercial drinks of that nature contain refined sugars, food colorings, additives, and other chemicals, which aren't good for you.