Repair a Ruptured Hydration Bladder with a Vacuum Sealer. Good link to keep just in case.
How to Tame That Noisy Hydration Bladder. So how does one get rid of that annoying sloshing sound? By simply removing the air from the bladder! "Turn it upside down and use the tube to suck out all the air." Great advice from Brian's Backpacking Blog.