If you exercise, whether you are training or competing, it does make sense to eat or drink carbohydrates if the duration is long. Even supplementing with protein can make sense if you exercise for many hours.
But you cannot do without electrolytes because of two quite important reasons. During exercise you risk sweating out electrolytes and the electrolyte level becomes too low.
That may be challenge as electrolytes helps you in staying hydrated and turn over the energy you digest.