The genius move I heard of was to throw a few 5-gal jugs of water up in your attic (!!!). It's relatively shelf-stable, standardized size, and "in case of emergency" you can even use it as a gravity-flowed spout to fill smaller containers below.

I've taken to trying to have a minimal set of 4 one liter steel water bottles hung in the closet (grab + go) all the time. So convenient to be able to "just grab some water" on the way out the door, and is the start of a solid emergency prep station.