Polar bottles also have the removable valve. Usually I take the valve off, put it on one of the tines on the top rack of the dishwasher. It cleans it quite nicely. Also, any common sense tells me to rinse the bottle when I put anything other than water in them. As banerjerk says, 10 seconds of hot water will take care of most gunk in a bottle. Also, it helps to not put them away wet.