I had a small pickup truck and had installed a speaker box between the driver and passenger seat. The box had an air release hole in it for bass. I had modified the hole to perfectly accept a beer bottle. If a cop was behind me, I would just drop the open into the hole where it would land on a coaster inside and not spill. When the cop passed, I could reach a finger in there and pull it back up. Never had a DUI or open container infraction.