I had a bunch of MREs (Meals Rejected by Ethiopians) left over from my days in the service
. They were sealed in impenetrable, welded shut, thick plastic bags that are everything-proof. They can be eaten hot or cold, but hot is better. Some meals
require hydration, but everything needed is in the bag. They are designed for an 18 year old kid in the infantry toting a 60 lb rucksack, so the calorie count is high--around 3000. Mine are still somewhere in the boat, probably the bilge
, but they'll keep. They would keep forever in a life raft.
Guess you can buy them in a military surplus store. There is a much better variety of meals
than there used to be, and they come with chemicals that are mixed to provide a heating
source when required.