re: A guy told me that before he stopped drinking, he was killing a fifth of Jack a day.

I have worked with a handful of functioning alcoholics over the years but two of them stand out over the others.

1) while at work he had a cup of coffee and a cigarette is his hand almost none stop. He would have work and but a case of Natty Lites and kill it before he went to sleep, everyday. Doctor finally told him he had diabetes and to quit drinking.

2) I personally witnessed him suck down a fifth of rum at a Christmas party in just a few hours. He would also buy a new handle of cheap Ron Rico rum at about $10 a handle every Thursday at lunch and drink better than half that night and still make it to work on Friday.