I could put one on each side, dad had an old car that the seat was a cement block so I guess it would work.
I managed to use a wendys cup once while driveing a manual transmission, with no curise control. I had just worked about 20 hours straight and drove a few more on the way home. I drove on for a while holding this cup wondering what to do with it and being very tired wasn't thinking when I thought it would be a good idea to roll down the window and try to dump it out. Of course the airflow blew it all back on me and all over the side of the truck. I looked really funny at the gas station when I finally found one to stop at using the window squeege on myself and the side of the truck.