I recently read a fantastic book called The Name of the Wind, it's sword and sorcery stuff so if it's not your scene, I understand, it usually isn't mine either, but it's a fantastic read.
To the point; the protagonist of the book happens to play the lute at local drinking establishments and describes a neat little "con" that he and the barkeep would use on patrons. Whenever an audience member would insist on buying the performer a drink, the performer would order a specific, unique sort of beverage, which was really a code word for water, and at the end of the night, no patrons were offended, the music didn't suffer and the barkeep and artist would split the take.
To the point; the protagonist of the book happens to play the lute at local drinking establishments and describes a neat little "con" that he and the barkeep would use on patrons. Whenever an audience member would insist on buying the performer a drink, the performer would order a specific, unique sort of beverage, which was really a code word for water, and at the end of the night, no patrons were offended, the music didn't suffer and the barkeep and artist would split the take.