clean the inside of the drinks hose of your camel back
Real men just drink the bacteria.
Keep your camelbak in the freezer after every ride (empty obviously). Done this with my 2nd bladder and its lasted way longer, with no ming!
I put the bladder in the bottom of the fridge and just leave it there. Sometimes, one has been in there for a few weeks and has always been fine.
One thing I always do though which may help, is never have any air in the bladder, just fluid.
Before I put the full bladder in my ruck sack, I suck through the tube with the outlet on the bladder at the highest point, this makes me suck a load of bubbles and air but no liquid. An added bonus is the fluid doesn't slosh a bout whilst I'm riding.