Baked beans- energy rich, easily stored and very cheap (29p a can). Baked beans can be eaten cold right out of the can if needed.
Corned beef- this is another versatile food. It is relatively expensive at �1.19 a can but it may also be eaten cold. Corned beef makes a good curry or it may simply be added to pasta. It would make a welcome change to a diet of rice and beans.
Fruit juice- this is highly portable and will keep your strength up if you are unable to eat. Fruit juice may save your life in a flu epidemic.