Apropos of nothing, last week while I was shopping at Wally World I noticed they had the Bridgeford MRE/survival sandwiches in stock (the BBQ beef ones). Another item that's not super healthy, similar to fast food nutritionally. But I figured one couldn't kill me so I got a package to try. IIRC the shelf life is around 3-5 years depending on the storage conditions. They're quite a bit of bread and not a ton of filling but they're really not bad, akin to something you'd get at a gas station or truck stop refrigerator case. You can heat them or eat them cold; I ate them cold since that's what I'd do in a pinch. They'd probably be much better warmed up.

They're not in quite the same category as lifeboat rations that will keep in any conditions for several years, but they might be a good option for something more like actual food.