crazy idea!

[Espeefan]

If you could find yourself a small enough thermos bottle, all you would have to do is build a tank trailer to fit it. The insulation part of the project would already be done for you. Or like one of the canteens that RCT posted, which already has a insulation outer cover already on it. I think those can be purchased separately too.

Otherwise, I'd stuff a bottle inside the tank trailer and fill the surrounding air pocket with Great Stuff spray in foam. Just be sure to allow for expansion. Maybe leave a end cap off the trailer so the foam could vent out.