I like the milsurp Jerry cans, and a funnel. Honestly, the tube spout is just a bad design. (IMNSHO) You have to perform Selective Compliance on a vertical hole, with gallons of fossil fuels sloshing around on the other end of the nozzle. No lock coupling, just a human being, who's used to doing this at the gas station with teens of feet of spring loaded hose, the pump bolted to the ground behind them, and a re-fueling bay with a meter on the front of it.
Then again, I was taught Hydraulic Fluid Power Systems by the Army. That hydraulic fluid? Yeah, 5 gallon jugs, or 40 gallon oil drums with hand pumps. Just to top off the hydraulic fluid in the reservoir.
And a gooseneck funnel. Quite possibly a Driver's Ed graduate civilian that can't change a tyre, because they can't figure out the Jack/Points. I just kinda have to troubleshoot the potential points of failure, and remember all the people I've seen going down the highway with their gas cap hanging from the lanyard. I've seen one with the fuel door closed, and the fill-cap hanging from the bottom edge of the access panel.
You can't make anything fool-proof, they'll just come out with a more advanced fool.