What you put in your pack for food depends on what you like and what you can carry. If you are sticking with the bare minimum than this is what you need: These food ration squares are intended to keep fed for 3 days. Tastes like a powdery cookie I think. Not awful, but not that tasty BUT you will live:) They have different kinds and are about $7. They also have individual flavored calorie bars that taste similar and are $1 each. The great thing about these are that they can be stored for a lot longer than regular food like granola bars.
You can also try Life caps which are intended to keep you full by taking 3 caps a day.