If you are presented with a bottle of frozen water, what would you do with it ? You need to turn it back into water and get it out of the bottle. How will you do that ? What equipment will you need ? How long will it take ?
In a vehicle with a working motor I'd just strap it down somewhere in the engine compartment. It shouldn't take too long, I'm guessing maybe 15 minutes? I'd love to test this and come back with some numbers, but I think it's too late in this winter season. But you newer know, we might have more cold spells coming.
Or you may choose to include a stove with your vehicle kit.