Buying sachet or bottled water in the store when we are out of drinking water is a very good idea. But come to think of it, if you're out of drinking water in midnight, it won't be possible to locate a shop or store to get the bottle on sachet water. Well, in my own aspect, I do fetch water from the tap and preserve it inside my room in case of emergency because we may run out of water or noticed. You have a detailed post here @imohmitch.