I was at dublin airport bar and the quiet old mn next to me got a straight whiskey. He picked up the stainless steel jug on the bar and poured the contents into his glass, thinking it was water. It was milk, for coffee. Thinking nobody had noticed his mistake he tried to pass it off as if he loved milk in his whiskey and took a sip. As he did not love whiskey in his whiskey, he places the glass on the bar and walks away, too embarrassed to admit his mistake.

It was funny.
Anything similar?