The car will then be unable to start.
Nothing. The battery is sealed an no harm will be done.
it will arch out and melt the knobs on your battery and your cables
they have to be recycled and they wont work.
THE BATTERY WILL GO DEAD
You will shorten the life of the battery. Only add Distilled water to a battery.
get a new car
you have to fint a way to get it out
If you explode you die and the same applies to a car battery.
you can hook a car radio directly to a car battery or even a car battery charger with out problems, I have done it myself, the only thing to remember is that it needs to have 12 volts and the polarity (+ -) needs to be correct.
Car no go.
If you use too small of a battery in the car, there might not be enough amps to start the car. You could also damage electrical components in the vehicle.