Many, many years ago one operator I worked for would overnight, away from their base, aircraft & crews on 'split duty' FDP's.
One particular Captain, as good an operator as he was, was known for liking a beer, as I like a beer myself, and it was known that he would drink on these overnight split duties in hotel bars, the 'split' part of their FDP in the hotel might have been 8 ish hours.
This was in the far more relaxed 'bottle to throttle' days, nobody worried about a few beers the evening before, however there was an occasion when this individual stuck his oar in, as if he was so 'squeaky clean' professional, when it was not required, targeted personally at, me and that was the opportunity I took to bring it to the management's attention that he regularly drank whilst on a Flying Duty Period.
It hadn't been something that had occurred to the management and, regardless of the blood/alcohol level when one arrives at the airport to operate, if one is on a split duty then one is on a continuous FDP whether it be in the aeroplane, a hotel or wherever and even a sip of the weakest shandy is drinking whilst on a flying duty.