Ghengis has the right answer. I have seen this problem twice in my career and have had the difficult task of sorting out the messes involved.
The Captain DOES have a problem that is probably alcoholism in some sort of developed stage as he is apparently not even careful enough to and hide his problem from others. This sort of behaviour is certainly noticed by bar staff and night porters and WILL out eventually. However, the potential seriousness is such that immediate action must be taken to ensure that he will not fly again until the illness (for that is what it is) is cured.
The fact that the pilot woks for "a small outfit" should make the task of a closed door interview that much easier and, I believe, any Ops Director or Chief Pilot will take seriously your friend's concerns. These days, one would expect the OD or CP to help, not hinder. The CA Medical Branch are up to speed with this one and should then become the primary source of help.
Hiding it under the carpet is not an option.
The BALPA PAG group, whilst a grand bunch should be the second line of help for this unfortunate pilot. The company MUST be aware.