I've got the Bird Butler water bottle - it's no ordinary water bottle! Attached on the outside of the cage, all pvc and hard plastic. Super easy to detach and clean, and none of my birds have had trouble learning to use it. However, Tiki Bird the evil galah did spend the first month standing on the valve and watching the water empty onto the floor of his aviary. Eventually he got tired of doing that and now drinks from it like a normal bird (or at least as normal as Tiki Bird can be...) Here's a link:
Birds, Etc. - parrot nest box and breeding boxes and Bird Butler water bottles for parrots