Oatmeal, Grape Nuts, and Granola.
Oatmeal is the easiest on the stomach and can be eaten with milk or cooked with oil.
Granola has the highest fat and protien content, will stick to your ribs the best, and can be browsed on as a snack. But, it is the hardest on your stomach.
Grapenuts is halfway between the two being more satisfying then oatmeal, but easier on your systen then granola. Prepare and serve it like oatmeal.

Add honey to your kit for more quick energy, and it has an indefinite shelf life.