How would you advise a friend who you suspect has a problem with alcohol?

That's a tough one. All you can do is talk to him about it once, tell him what you see, and how you feel. Remember, this might turn into an argument because people with an alcohol problem will defend their drinking with everything including the kitchin sink. Sadly, that is all you can do because you can not help someone who doesn't want to be helped. All you can do is be a friend and be there for him when he hits rock bottom, as most alcoholics do. What he has is a dependency problem for the simple fact that he believes he needs it just to go to sleep. If he chooses to listen to you and try to change, you can go out running every night, that way he comes home tire and ready to sleep. If not running, then a good strong work out. Either way, he will need to redirect his energy else where. Trust me, I've been there. So good luck with your friend, I wish you and him well.