The claim made by sport drink manufacturers is that their product is superior to water. It contains electrolytes and sugar to replenish what is lost during exercise so that it can boost performance. Depending on what your goals are, these drinks can help you.
If you're trying to lose weight, these drinks are bad because of how many calories they contain. To lose weight, you need to burn calories while you're exercising. You burn about 100 calories for every mile you run.
One serving (8oz) contains just about the same amount and each bottle usually has 2.5 servings. Even if you burn off all that sugar, you'll just be maintaining your weight, you won't lose any.
The best drink to help you lose weight is plain water. It has no calories and will keep you hydrated. If you can't stay away from sports drinks, try the ones that have half the calories. Though they are still high in sugar, using them as a substitute is a step in the right direction.
If on the other hand you're trying to increase your performance, studies have shown that people who workout longer than 60 minutes can benefit from these sports drinks. If you want to have more intense workouts, run faster or lift more weight, then a sports drink can help you out.