This will be a text tutorial as I have no capture equipment.
What you will need:
A Personal vehicle you don't mind getting replaced
Find a supercar (I used an Infernus)
Get your friend to get his tank.
Park the supercar near the garage but not close enough to be blown up.
Go into your garage.
Put passive mode on
Get in the car you don't mind replacing
Drive out and as soon as you see your garage open have your friend ram and crush the car in the first few seconds. Tell them when YOU see your garage door open
If done right you will be able to get out of the car alive and run to the parked car. You will have no HUD
Get in the parked car.
The game will spawn you around the corner because your door is blocked and the time for the cutscene has ended.
The car should now have a tracker and can be driven back into your garage or taken to LSC
If done with a free car like an elegy you cannot sell the insured car