I wish I had an answer
I have a friend I have known since 1978. He has had a drinking problem for years, and of course I used to drink with him. Over the years, many people have tried to get him to stop, me included. His sister did an intervention on him. He went to treatment. It did not last. He has had a stroke. Yet he still smokes and drinks all the time. I am sad to say that I and others have given up. I am still his friend, I guess I always will be. But I don't try to get him to stop anymore. He will stop when he is ready or if he has some serious health issue again. Meanwhile, I try to be an example and maintain my own sobriety. That is all I can do really. You can't make somebody stop drinking. Sorry that I don't have a better answer.