Ok been here done this, I still carry a 45 Canteen hunting these days, what I do is one of several things, drop some house hold bleach into it with some water, give him a good shake, let him stand over night and then drain and rinse a few times and let him dry for a day or two this will remove the foulest of pongs from a canteen, or you can use a good denture cleaner Steradent or similar you know what people clean there false teeth in, another is baby bottle cleaner which we use to clean our bottle before filling with fresh home brewed beer, great stuff. I have done this for 20 years and never got a crook guts yet from it, water sterilising tablets work too, the trick it to leave the bottle dry and open when not being used.
I should have thought of the denture cleaning supplies... (speaking from Experience... nuff said http://www.usmilitar...tyle_emoticons/default/w00t.gif ) Like I said before I do have two SS canteens and I'll use them for my public displays or reenacting. I dont know why but I DO like the look of the M1910 canteen... metal cap and all.
Thanks everyone for the ideas...