I had 2 interventions in my life and neither worked. In fact, they made it much worse for me.
I suggest that you go to AlAnon and learn a bit about alcoholism before trying anything (btw, AlAnon is not AA, but is a program to help non-alcoholics understand what they’re dealing with.)
Your friend is lucky to have you. Don’t give up on them. It truly is hellish, and they’ll need your support.