I use the baking soda method. I put just enough water to form a paste with the bakind soda and then just scruch it around.
I've also used denture cleaning tablets.
BTW, don't leave your Camelback in your gear bag for 3 days in the back of your truck in 90 + degree weather! YUCK!
Had to soak in for 2 days in bleach! Still Yuck!
L8R
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger