I got a bunch of the double Mosin cans, and several of the singles, in trade a while back. I cleaned them out THOROUGHLY with 409, then Easy-Off several times and then boiled them for 20 minutes...I figure this would eliminate all traces of anything that HAD been in them. One set is now, with some modifications, a salt and pepper shaker.
One of the singles holds about two cups worth of instant coffee or powdered drink or sugar...all kinds of uses.
If you do re-purpose them, remember to remove and replace the waxed cardboard seals in the caps.