This can easily be done in a Custom Event. Create a new Championship, 1 Event, 1 Stage.
Select any Stage you're comfortable with driving. I would recommend a longer stage so that you can build up a large lead before you attempt to spin your car.
Set the AI difficulty to 1 (Very Easy).
At any time in the stage spin your car, this can easily be done by using the handbrake and turning at high speed. If you're in a Rear-Whee-Drive car you can also use full throttle after a slow corner (without Traction Control) to easily spin the car. Do this 3 times (4 to be safe).
Once you've won the Stage and continued on past the podium it should unlock.