I have a 2 gallon bucket from TSC, two nipples. I put the bucket inside the coop in the winter and add a fish tank heater, it was plugged into a cube so it only came on when Temps were low. Worked great to keep water from freezing.
I have used cups and vertical nipples.. and it really depends on the breed of chickens you have. I can't remember for sure but I did read some dont do well with nipples...
Cups are great for summer but nipples are less likely to freeze if inside the coop in the winter..