You will need a big hat!
First you should look after someone who just ordered a shot (and are sitting by the bar). Go the the guy/girl and put your hat on the shot.
You - I bet i can drink your shot without touching the hat. And if i fail i give you a dollar/penny (or whatever you have).
The girl/man - Sure
Now you should bend under the table and make a drinking sound, and end with an *aah*.
You - Look under the hat if you don't belive me.
Then you drink the shot after he/she lifts the hat.
Now order another shot (try to order the other one quickly).
Now put your hat on the other shot.
You - Do you think i can do it again?
He/she - Yes/No (does not matter)
Now you just lift the hat and drink the shot.
You - Oh, i lost!
Now give him/her the dollar and say: Thank you for the shots.
Now just walk away
.. not bad