I've used camelbaks while hunting for years. I typically rinse em well with fresh water and prop them open to dry after every use. Then once every few weeks wash it with warm (not HOT) soapy water and allow it to dry. To recover yours from slimeville I would probably mix some rubbing alcohol with water and shake it up real good.
You can't just refill it and drive on every time you want to use it or bacteria and whatnot builds up and gets out of hand..