Ultimately you can do nothing more than offer support. Most times that's nothing more than just being open and available to them, but never condoning the actions that they keep failing at. It's called accountability. It takes 2 people to do it. So if you find after a while that you are the only one actually participating, it may be time to sever your connection to them if they are on a self destructive path. It doesn't mean you disown them, but you keep some distance from them because that destructiveness can and often does bleed over onto the one trying to help. Bottom line is, the friend has to do one of 2 things; A) they make a determined effort to clean up and stop drinking. (Less likely) There are ways that they can stop and change their life. B) they have to hit rock bottom HARD before either making a concerted decision to change, or they may run out of chances, if you get my meaning. It sucks and it's rough either way, but as a friend, those are really your only options.