Nothing. If a person abuses alcohol, then he is an alcoholic. Even if a person drinks 1 time a week but regularly, this is already 1 stage of alcoholism. Your father is sick. And until he wants, no one can convince him or force him to stop his illness.
I'm afraid not. As a rule, an adult commits such actions consciously, and if the amount of alcohol consumed exceeds all limits, he can harm himself and his loved ones by such behavior. Unfortunately, the consequences, however severe, are not taken seriously.
You can try to talk, negotiate, ask ... But sometimes it seems to me that as long as a person does not get a good shit (does not get into trouble because of his habit), life will not teach him anything.