https://titanfueltanks.com/products/titan-trail-trekker-ii-4040287
I'm sure you can put water instead. There's a printed gas label on the side, but you can place a water sticker over it to let others know it's content.
There's a few mods that you have to do to make it fit properly since it was built for a jeep 5x5 bolt pattern. I got a pair of 5x5 to 5x120 25mm wheel adapter, which happened to be a smidge too thin. I ended up chopping the wheel studs on the tank and got shorter lug nuts and now it sits perfectly. I other than minor mods to get it fully functional, it's awesome. I remove it when I'm not off roading.