A sports or energy drink, fruit smoothie, or light beer — each serving contains about 100 calories. Yet these beverages don't satisfy you the way 100 calories of food does, so they're a waste. Other liquids may be high in sodium and carbohydrates, which trick your body into retaining water, puffing you out. Water, on the other hand, has zero calories and carbs and little to no sodium, making it the perfect slim-down drink. And strangely, it actually helps flush out excess water weight as well as jump-starts your metabolism. If it's just too boring, add lemon wedges or mint leaves.