This is a classic proposition bet. You challenge your mark to a drinking game. You claim to be able to drink 3 pints before they can drink 3 shots. There are two rules to stop cheating; you can't touch each other, or each others drinks.
This seems so impossible you can ask your mark to allow you to drink your first pint and place it back down on the table before you both begin drinking for real. They will oblige as they can easily drink 3 shots before you can drink 1 pint.
After you finish your pint, turn it upside down and place it over one of your marks shot glasses. They might try and pick up your glass, remind them of the rules, they can't touch your glass. Take your time drinking your pints, and enjoy your money