Having drank many gallons of water from those canteens,I will tell you, the plastic itself has a certain offensive odor when you open them. I dont know why, or what, but there is an odor in all of them you will never get rid of. I have served both Air Force ( short time ) and Navy, both with the green plastic canteens, and If its the odor I just realized that you are talking about, then it is permanent, and you will never get rid of it. They come that way. Kind of a musky... warm smell? The best cure for that is not to inhale while taking a sip. Thats how I solved the problem with all of my canteens.