I'm sure the "Alcohol" comments are all in fun. Don't worry about that.
On a more serious note however; One drink and I lose complete control of my diaphragm and vocal chords with regards to singing. Actually, as far as entertaining goes, everything suffers if I take a drink.
I know , I don't give the mechanic a wee hauf before he works on my car and I have to wonder sometimes when I hear employers offering the entertainers free beer as part of the agreement.