This is something a friend of mine did 10-15 yrs. ago after he had tried everything he could to rectify many problems with a new car (American made)he had purchased from a dealer.
He visited a sign shop and had two magnetic signs made that read: This Lemon was purchased from xxxxxx Chevrolet/Cadillac. He placed them on each side of the car and drove it for a few days around town and the dealership. He then parked it in the dealers lot while he spent a few hours there supposedly looking at other vehicles.
Within one week they had bought his lemon back and made him a heck of a deal on another car.