I don't clean mine, I re-fill them when I get home and then leave them in the refrigerator ready for the next ride. Haven't noticed anything unsightly or smelly yet.

But, if you do choose to clean, there are lots of suggestions here:

http://forums.teamestrogen.com/showt...aning+camelbak

and here:

http://forums.teamestrogen.com/showt...aning+camelbak