While making a cocktail (alcoholic beverage) for someone, you use your erect penis to stir the drink.
Bar Patron: "One Jack and Coke please."
Bartender (or twisted friend): "Coming right up." (You then whip out your erect cock and stir the poor bastards's drink to perfection). AKA the "Dallas Dangler."
Bar Patron: (Sip) "...Ahhh, that's a STIFF Jack and Coke!!"