You never know what you'd do in every situation.... But for this situation, I'd try my best to find an open space and STOP. Get out, get to safety, call emergency, and get far away from the fire as possible.
Normally a person who has a coach with a toad probably would have comprehensive on both. Nothing is worth your life.
Of course I didn't see the fire either.... All would depend on SO many circumstances.
If it was reasonable enough and you are agile/fast enough, you could throw on the 12V pump, hook up a hose (if you have an exernal adapter) and start spraying it with fresh water. Of course ALL would depend on where (on both the vehicle and location) and how large the fire is.
Make SANE, calm decisions if possible. Always call emergency or have your DW call while you pump fresh water on it.