As a person who has used both of them water and fuel cans. Your better off selling the water cans than ruining then with fuel. I can tell you how pissed off you'll be using on for water after some D... A.. used one for fuel. Much less some of the other problems that come with that happening. Probably why the military is still stuck issuing bottled water now.
The plastic seems to be the same just the threads for the caps and lack of vent tube in it. (Water can)
FYI: the part with D.A.. Ref is from being resupply of water that way in Army
reason I have multiple water filters now.