I honestly think the best thing you can do for a sudden immersion in a "low risk" (not driving on ice...) automobile is to be mentally and physically (more on this later) prepared for the situation.

This guy didn't do anything crazy (though didn't have to contend with windows) and made it out: https://www.youtube.com/watch?v=0D5PRDQPMOE

So I'd be sure to be aware, physically fit, and very comfortable in the water (do some scuba diving or snorkeling). If you can, take a ride in a tank. https://www.youtube.com/watch?v=ad_8-RVIy4w

People can technically go into 30 degree water and make it out, and if you run back to the road and get in a warm car in your underwear, you'll probably be OK. https://www.youtube.com/watch?v=EF1V8HFfpTE


This assumes you make it out of the sinking car though. https://www.youtube.com/watch?v=QIx719_oer0

Something like this is always a good idea: https://www.amazon.com/dp/B073J92G1J/ref...59-01df5dfa83f2

I personally probably would not carry a kit like the one you contemplate. At most, if I was driving on a frozen lake, I'd keep my windows open and my spareair handy.