There used to be a pub in the UK near the Tower of London that used to get a lot of footfall from tourists who would never return. They were prosecuted when it was discovered how they would have bowls of spirits, and if someone asked for a vodka and tonic, for example, they would dip a glass in the spirit and pour the tonic so the customer tasted the spirit from the rim and assumed they were drinking the spirit. I wonder how many got placebo drunk?