It is highly likely that he is drinking again, however at work I kept asking one of my clients if he was using solvents - similar smell to cheap white cider, but more chemical somehow. I eventually got to the point where I believed him (believe me this is rarer than you think in the hostel) and tried to work out what else it could be. He was diagnosed a week later as diabetic. If he checks this out and there is no problem, he is definitely drinking. The smell of alcohol is gone within three weeks max.