The way we put out battery fires at our RC airplane club is dump a bucket of sand over it.
So for a full sized car, get a bucket loader, scoop a bucket full of dirt and burry the car.
I watched a video of a fire department showing how they handled burning cars. They throw a huge specially constructed blanket over the car and contain the fire within. The blanket is fire resistant. For gasoline fires it extinguishes the fire by denying oxygen. For other fires, it contains them so they won't harm surroundings until they extinguish themselves. These blankets would be ideal for EV fires.