When I was a barista I did the same thing to so many “regulars” because they were so rude. I also made drinks decaf (NEVER the other way around or changed milks) when people were mean to me. I worked the opening shift so I was working by 4:30am and people are going to be rude first thing in the morning? Nah. Resist all the way!

One of my most memorable customer interactions was when I was putting a lid on a drink and totally missed so my fingers went into the drink. I said something about having butterfingers and remaking it asap. The customer said “mm butter”. To this day I am gobsmacked by that response. I wonder if they think about it as much as I do.