I only use water in my camelback. Every once in a while, I use something called HydraPure. I like that it doesn't leave a taste in the bladder if you get it rinsed completely. TE sells it. Here's a link http://www.teamestrogen.com/products.asp?pID=4038
It is an anti-microbial cleanser for hydration systems.
  • a superior anti-bacterial, fungal, viral, and yeast soap
  • scrubs growth and build-up
  • cleans microorganisms with no after taste
  • designed to be safe and effective with drinking bladders