I say he was drinking and then, somehow, ingested a foreign substance which is not related to any of the many naturally occurring alcohols, and probably not methanol.
REASON: Methanol does not cause sickness, normally, this quickly.
I realize that I am not a forensic pathologist, and I have not seen the lab results, but it does not sound like an alcohol issue to me.
This must have been caused by some other drug, or adulterant, either intentionally provided to him, or through some other misadventure.
If I were to hazard a guess, then I would think something related to heroin, perhaps.