I use tend to avoid gels and such like and concentrate on using easy to eat and digest ‘normal’ food like peanut butter sandwiches, jam Sandwiches cut up small into bite size pieces. also Pringles, popcorn, banana’s and I make up my own rice cakes.
Make sure you hydrate properly don’t over hydrate and flush all the electrolytes outs of body and conversely don’t drink too little. As with the food I tend to avoid or at least minimise the use of energy drinks, if I do use them I make them up quite dilute.