The phrasing of your question is a bit unclear, but if you're asking about the first person to "ride" in a car, it would be difficult to pinpoint a specific individual. The early development of automobiles involved multiple inventors and pioneers.
However, if you are referring to the first person to "ride on" or modify a car (such as hot rodding), the origins of hot rodding are often associated with young enthusiasts in Southern California in the 1930s. The exact "first" person or car modified in this way is challenging to identify due to the grassroots and informal nature of the early hot rod culture.
I would say Benz the German was the first to ride a car.