I don't use a dishwasher, either. As long as I remember to rinse the bottles out after each use, they are fine. But forget for just one overnight in hot, humid weather, and ICK!! Black spots that don't rinse out in the morning. I fill the bottle almost to the top with cool water, then top it off with bleach. Invert the top of bottle into the bleach solution, too. Let the bottle sit for at least 15 minutes, and presto! Mold is gone, bottle is sanitized. I rinse it well and have not had a problem with bleach taste remaining in the bottle. I've used the same water bottles for years, usually till I lose them or until the top wears out and leaks.
Lots of great ideas in this thread!
annie
Time is a companion that goes with us on a journey. It reminds us to cherish each moment, because it will never come again. What we leave behind is not as important as how we have lived." Captain Jean Luc Picard