Shih tzu recently won't drink from hanging hanging water bottle?

I'm thinking it's the plastic...plastic retains odors and often, bacteria, and it turns the dog off (after being in use for 3 years, I'm sure this applies to yours, even if you do wash it regularly)...they all want fresh, cool water (I'd say that's why so many prefer toilet water). I suggest switching to stainless steel bowls...it's easy to keep clean, inexpensive, and the dog won't get grossed out by bad smells.