I'm contemplating using one of these as an under-vehicle tank. I know that a purpose-built tank would be better, but for the cost, this would be a relatively cheap experiment. The pic above makes me think that laying the tank on its side would not cause a problem. I was thinking that a vent line and the out-put line would be worked into the cap somehow.
The military water cans and the gas cans are very different animals and the water cans cannot be used to store gas. The Scepter gas cans are so expensive now that it could actually be cheaper to buy a purpose-built second gas tank for your vehicle