In fairness, the only thing many people will lack is water. It's not an exclusive stash, but in addition to what's in your cupboards.

You can get 10L or 25L quite cheaply. 1 should do per person, maybe with an extra for cooking. Or just grab some big bottles of water.

A hand cranked flashlight, candles and lighter are all a must anyhow, for a power cut. It might also be worth having a cheap camping stove tucked away.

Food wise. It's just a big bag of pasta or rice, along with some cans/jars to make it pleasant to eat. Throw in some hiking snack bars and you're sorted.