Nope, I'm not kidding. I use bleach to clean my waterbottles, and have been doing it for years. You use a small amount of bleach mixed with dishsoap to wash them out, then you rinse and rinse and rinse. Then you wash them with just dishsoap, and rinse some more. Then you let them air dry ....... and by morning the bleach smell, is gone and your bottle is as fresh as a daisy!

I suspect it would work the same with with a camelbak bag.