Nothing here is ever written about nutrition and the energy it gives. I read an article that says that a sprinter wil avoid fats. They take too long to be converted into energy. In fact they will be detrimental to the athletes performance. Wholemeal bread and products the same. White bread gives energy within a short time, wholemeal doesn't. Do we have any experts out there. To make it clear we are looking at the right food to eat or drink that will give instant energy when needed. Some of you tennis players will no doubt remember Ivan Lendle who brought the bannana into focus by taking a few bites at the change of ends.

Fats do take longer to convert to energy. For most people, the time taken for food to be converted into stored glycogen (the fuel for muscles) is not a factor. For an athlete, glycogen is stored in the liver and in the muscles. It takes about 20 miles of running for these stores to be depleted (hence the 'wall' in marathon running).This is unlikely to happen for a dancer or a sprinter. But for a top tennis player over 5 sets, it could. Hence the banana, which also provides important minerals to help keep the muscles working.
I wouldn't recommend white bread under any circumstances (except i believe it can be use to erase a soft pencil mark). Glucose drinks are best if you want really fast energy boost. Quickly absorbed and converted to glycogen fast. (chocolate is good too But to be honest, as a dancer and a mad exerciser myself, my view is that it's best to eat a good balanced natural food diet as much as possible.
Eating fast energy release foods (so-called high G-I foods) can stimulate insulin production to convert the sugars to stored fat.