I have asked random folks for water and they have always been happy to give me some. One time we went up to a house in a tiny town and asked for water from the spigot, they were happy to give us some. Another time I flagged down a motorist in the middle of nowhere, she was very happy to give us some bottles that she had in her trunk. We camped at a rest stop in a remote area (only flat spot around) and when some cars stopped to see the view we asked if they had some spare water. One guy was very happy to help us, as someone had helped him out on his road trip a few days before.