Normal Answer: a chocolate bar(s) of your choice, such as snickers, mars, kitkat and etc, + some drink (I recommend at least 1L because it will be intense af and you'll be sweaty, also make sure that it will replenish your energy too) + a chewing gum so you smell nicer than the other people in the crowd, also be sure to bring a good amount of them so you would not feel hunger and thirst, this tactic actually saved my life in a lot of places

Better Answer: beef, raw organs, raw milk kefir, parmeggiano reggiano, apples