Because we sweat during exercise it is very important to re-hydrate your body by drinking before, during and after exercise. You also lose salts and other minerals in our sweat and so drinks containing electrolytes and carbohydrates can help you to keep your fluid-electrolyte balance and continue our exercise performance. However as far as I am aware, the evidence to support drinking drinks with electrolytes in them isn’t very strong.
How much you need carbohydrate and electrolyte replacement during exercise depends on the exercise intensity, duration and how much you sweat. Sports drinks like Powerade can be helpful because they contain carbohydrates and minerals which help to replace both the water and the calories you lose when you exercise.