Hydration bladders get quite horrible looking after a few uses with electrolyte tabs. There's something in them that stains the plastic. Hydration bladders can also get a bit yucky if energy drink is left in them after use, so its worth giving them a clean out every now and then to keep things fresh and clean. Cleaning your hydration bladder is really simple, you'll need at the very least some Milton Sterilising Tablets. Also a Hydration Cleaning Kit is a good idea too too to clean the hose and nooks and crannies in the bladder. First off rinse your bladder out with a bit of soapy water, a sponge and a little bristle brush, to get rid of any residue or build up inside the hydration bladder and hose. Rinse out all the soapy water, pull the bite valve off the hose if you haven't already done so, and place both inside the bladder. Add one Milton Tablet, fill the bladder up with warm water and then close it. Give it all a gentle shake about to free up any air bubble and then leave to soak over night. The next morning you'll have a nice clean hydration bladder, just rinse it out and away you go! Don't worry about the slight chlorine smell, it goes after one us and doesn't taint the taste of any drinks you put in the bladder. Yucky & stained Hose cleaner! Hydrapak Hydration Bladder soaking away nicely.