I bought one of those alcohol testers that you blow in and would make him blow when I suspected he was drinking.
I used to find his water bottles (what a hassle for him to have to pour his vodka into the water bottles, then ditch the vodka bottle) and dilute the vodka with water.
I can't count the number of times we've gone to dinner and I haven't ordered a drink when I wanted one because I might tempt him.
I've taken his car to the grocery store just so I could rummage through his trunk and find booze. He usually kept it in his golf bag.
I asked his friend not have have booze ready for us when we came to visit. He found out and BOY was he pissed that I blew his anonymity.