I have a portable power station, it's a bit of an investment but it means I can boil the kettle or plug the air fryer in.
You can get canned food that is self heating, it isn't cheap though.
The PP's suggestion of a military rations is a good one. You get enough food / drink for 24 hours and because they are designed to be eaten by soldiers in the field they are high calorie.
Things that last a long time and can be eaten cold. Tinned fish (tuna springs to mind) meat such as Spam / tinned ham / tinned corn beef.
Tinned sweetcorn - mix it with the tuna.
Biscuits last for ages as does fruit cake.
If you can heat water then dried pasta, noodles, cous cous only need hot water pouring over them and leaving to stand.
Things from the freezer you can cook with hot water kippers (just put the pack in a jug of hot water and you can cook from frozen).
You can also have in the freezer, cooked meat, cheese, milk, bread, cakes, smoked salmon, then all you need to do is defrost them.
Things in jars, pickles, jams apple sauce, mint sauce (OK not great on its own) chutneys, olives.