Breakfast, lunch and snack ideas:
Granola, dehydrated milk, raisins
GORP (Good ole Raisins and Peanuts). M&Ms mixed in too.
Candy bars, granola bars, cereal bars, power bars (snickers make a power bar now).
Tuna in the Foil packs, Lots of different foods in foil packs now.
Bagels (My favorite with tuna, mayo and mustard)
ketchup, mustard, mayo in the fast food restaurant packets.
If you have a food dehydrator go nuts with it. You can eat very well like this.
There are books on this subject and you can also search online for hiking recipes.