Pat Sajak -- I Was Drunk on 'Wheel of Fortune'

Pat Sajak used to be WASTED on "Wheel of Fortune" back in the 80s -- this according to the game show host himself.

Pat made the confession during an interview with Dan Le Batard -- claiming in the old days, he would down "two, three, or six" margaritas at a Mexican joint near NBC studios during the show's 2-hour dinner break ... before heading back to finish taping.

According to Pat, Vanna was also guilty of drinking on the job -- but they've since stopped the mid-show imbibing tradition.