Some years ago, I saw a guy jumpseating get offered a First Class seat, as was I. He was a young regional guy, and new to the industry. FA asked if he’d like something to drink...he ordered alcohol.
FA mentioned it to the Capt.
Capt came back and said, diplomatically, “I’m sorry we won’t be able to accommodate you today.” He was sent packing...the look on his face was “what did I do?”
Technically, if a flight was selected for random drug screening, I’m pretty certain even jumpseaters are included.