Actually... according to wikipedia, F1 cars have a drag coefficiency of 0,7 to 1,1 due to all the downforce. But then we come back to what you mean by "unaerodynamic" because although an F1 car have a high drag coefficiency they optimise the airflow to create downforce.
If you by unaerodynamic mean aerodynamic chaos, like the designers doesn't really care what the airflow around the car looks like, then my best bet is the Schwimmwagen. It's also relatively light so if you can get it up to high speeds, chance is pretty high that you can get it to be really wobbly.