How come most people try to solve the no heat problem instead of the food that does not need heating problem?
Some stuff that can taste well even "cold":
Canned tuna + precooked canned beans + onion + salt pepper oil vinegar.
Watermelon (quite inefficient when it comes to nutritiom but tasty)
Bread + mustard+ hard cheese or certain types of sausages (especially smoked with low amount of water inside).
Most vegetables and fruit will survive 5 days if they do not have defects and you can keep insects away from it.