The first player spins the quarter on its edge like a top, and while still spinning, the person on their left calls heads or tails.
The person who spun the quarter stops it on the table.
If the caller is correct, he/she spins the quarter for the first player, and the first player must chug until the quarter stops on its own. If the player calls wrong, the first player spins for him/her again, and they must drink until the quarter quits spinning.
After that, the person on the first players left (the caller) spins the quarter for the one on his/her left and the game begins again.
If the person spinning for some reason fumbles the quarter before they spin it, they hand the quarter back to the person on their right and it is spun again for them so they may chug again.
This game has a high buzz level. Make sure there are plenty of extra drinks so they can chug the WHOLE time the quarter is going...