why would it be stealing? our church has a container in the lobby area (narthex, some places call it) that’s specifically for people to use to take water… it looks like one of those drink dispensers, you know with the little flip spigot? I have no idea if all churches have one, but I would guess yes, and the reason you haven’t noticed it is because it’s off in a corner and there’s not a huge line for it… though maybe there should be!
technically, any place you see selling holy water isn’t actually selling the blessed water - they’re selling the container and the unblessed water. sale of a blessed item removes the blessing, and selling an item for the blessing or increasing the price because it’s been blessed is simony and is forbidden. for example, I found a site selling water from lourdes, and at the top of the page it says that your order can be blessed free of charge before shipping.
(I wouldn’t drink it, though… you don’t know how long it’s been sitting there or if the container is clean, or even intended for potable water.)