Never drink anything from a dispenser you don't clean and don't trust someone to clean. Which, for me, is none of the ones in public/restaurants.

I'm probably a little paranoid though, I don't connect to the grid at all and filter my well for all the heavy metals and various bacteria in the groundwater around here just because I know eventually the shitty privatized/subsidized sewers and water in my area will go belly-up during the next infrastructure crisis.