Water bottles washed in the dishwasher is just a lazy feel-good, not a real cleaning. Being lazy and liking to feel good, I resort to the dishwasher. But just think about how the dishwasher works - spraying water around. A bottle brush and some hot soapy water is going to work much better. Once you have mold, however, you're going to need bleach to knock it out if you don't like your biology experiment.