If you are preparing for long bouts of exercise (anything longer than an hour), any endurance training or anything you need to recover well from such as athletic competitions, then eating before the event is advised.
The energy contained in the food you eat before sustained exercise will help the muscles continue to contract during your efforts.
Far from making you feel bloated or sluggish, some form of carbohydrate or sugary food will break down to provide essential energy.
That said, it’s not a good idea to scoff a bag of doughnuts and hope for the best. The best results are when the food has been broken down and absorbed so the energy can be used by your muscles. So steer clear of anything that takes ages to process. That includes fatty foods, high fibre foods and protein.
Simple sugars like pieces of fruit or sports drinks are ideal.
Eating before a workout takes a bit of getting used to and doesn’t suit everyone. If you’re doing a shorter workout, it’s better to eat afterwards.
Although replacing nutrients, salts and sugars is important, the most important thing you should keep in mind is fluid replacement.
Drink straight water, fruit juice, or carbohydrate-rich sports drinks to replace fluids lost during exercise through sweat.
My nephew is advised to eat jelly babies before a football match, so that's a very low-nutrient pre-workout sugar fix, but I bet it works!
I have never drunk anything except water or skimmed milk before, during or after a workout and I have always felt fine. These sports drinks are a complete gimmick.