First you have to get close enough (without someone reaching out and giving you a preppers touch) second 5 gallon isn’t going to burn for long so if you use the right inslulation you ain’t going to feel it. And lastly it would most likely be a waste of a valuble commodity (gasoline).
Specs for a shipping container look to be 2mm for side and end panels, and 1.6mm for the roof. IMHO, that’s not nearly enough to qualify it as “fortress” material.