Also thinking about battle, there could be a small carouse check for the intoxicated fighter that he could act disorientedly.
Flow
-I order my character to go some tile
-A meta-check decides whether it is appropriate for a Carouse check or not
---------If not the character goes to that tile
---------If yes Carouse is checked
-----------------Success: Character goes to that tile
-----------------Failure: A notification appears like "Gurbosh is too intoxicated and disoriented" and character goes to different direction
So basically, the effects would be both noticeable during walking through cities and dungeons (I mean if you feast and drink wine like there is no tomorrow in evil ruins, nobody is stopping you

) as well as with a small chance in battles. For people with weak stomach, after drowning their sorrows in high-alcohol Thorwalian beverages, it might be wiser to sleep at an inn and deal with morning hangover instead going out to slay a den of wolves.