Not sure I've ever seen a passenger car with a 120V plug. RVs, sure. But in a passenger car the usual way to do this is to buy a 12V inverter and plug it into the DC power port (colloquially known as the "cigarette lighter").No 120VAC outlet built in/hidden, and no factory option for it either.
lots of modern SUV / Minivans have it now
My former Ford CMax Energi had a 120v receptacle. Used it a few times to power my laptop.
the Mercedes ML series have 110v plugs in the rear seats, also Jeep has it too