I enjoyed the joke, even sent it on.

I store the small bricks of Ribina 10X200ml in the car.

http://www.britsuperstore.com/acatalog/Ribena_Ready_To_Drink_Blackcurant_10x200ml.jpg

I am not sure if you can get it in the US but it is a blackcurrant drink which has a lot of sugar in it and you will have something similar I am certain.

Because of the sugar the freezing point is depressed and it stays liquid to -5ºC or so and even when they do freeze the pack expands OK.

Another advantages are the energy value from the sugar, each pack has a straw attached and they taste good.