We have been asked several times the best way to clean out the 4 gallon easy fill drinker with twist cap. It is a bit difficult to clean since you can't access the inside with your hand. So how to clean?
1) Get a small bag of aquarium pebbles or some type of pebbles/gravel.
2) Pour a couple of cups of pebbles into the drinker
3) Put twist cap on and then shake vigorously.
4) Rinse and Repeat until the inside is clean.
The entire process takes about 5 minutes.