Hand sanitiser would be ok for short-medium term hygiene purposes, with wipes as a back-up. Dry shampoo works well, too, but to be honest I think that if people are holed up in a power cut they probably won't care too much about what they look like.
Clean hands matter, obviously, so large bottles of sanitiser seem a sensible option.
If there is not enough water to flush the loo, you can line it with heavy duty garden waste bags, cover with a scoop of cat litter after each use, then tie the bag and put in the outside bin until collections resume. I posted this on a different thread, but people may not have seen it. (wee in a bottle, and dispose of that separately).
Google says that water is safe to drink after the sell-by date, but may not taste as good, because of plastic leakage, but that as this is food grade there will be no harm done. Better a slightly plastic-tasting drink (you can always disguise it with a bit of squash) than gong thirsty, I think.
I certainly don't drink 3 litres a day, but can imagine needing at least that if toothbrushing/cooking (assuming we can cook) is taken into account. Maybe not 6 litres between us though, as we'd obviously cook two portions at once.
