Hiya
A lot of the calories in a pure fruit drink will actually be from carbohydrates, which are "better" because they break down slowly over a few hours. Sugars break down really fast, giving you a quick rush when you have lots of energy, then disappearing, making you feel hungry again.
Plus if you have excess sugar in your system, you are likely to convert what you don't use to fat, while if energy is released a bit at a time, like with carbs, you are more likely to just burn it.
Hope that helps
