Energy bars, some sort of meat jerky, soy nuts, other nuts, dried fruit like dates, figs, raisins, apricots. Pass up the stuff with added sugar.
Be sure to have lots of hydrating beverages along the way, water, diluted fruit juices. Cut back or discontinue things like coffee and regular tea which can be dehydrating.
Also, get a book or pamphlet that tells you about wild edibles in the region you'll be hiking. There are some suprising edible things out there, but it'll be depend on where you are.