Innervoice, I also have several of these and they will taste bad sometimes. The thing to do is use some cleaners like suggested in the rest of the replies to your post...lemon juice is good...the acid in it kills a lot of odors and tastes. One thing I do to combat the taste problem AFTER first use is try to always use bottled or filtered water in them...faucet water has little "thingies" growing all in it and loves to make the water bladder all slick and gooey..I have thrown them away for this offense before. Good luck and don't drink the water!