Most of us know what foods to choose - and which to avoid - when trying to lose weight. But the average American gets one-fifth of his or her calories from drinks, so it pays to take a look at the liquid refreshment you choose. It's especially important to stay hydrated when it's hot outside, so keep drinking…wisely. The clear diet drink winner is, of course, water. It's the best way to keep your body cool and hydrated, your tum...