Alcohol abuse can predispose to the development of diabetes by itself and due to chronic pancreatitis and heavy fibrosis and calcification of the pancreas.In such people,during alcohol binges recurrent and "prolonged" periods of unconsciousness are usually because of lack of Glucagon and alcohol per se preventing glucose release from the liver.
But you mentioned that the episode lasts for only 5 minutes and he comes out on his own"fresh and ready to fight".This is not the usual scenario with alcohol abuse!YOU ALSO MENTIONED CIGARETTE SMOKING.I would rather think in the lines of cigarette smoking causing "transient loss of consiousness" in your dad.
His chances of developing diabetes are extremely high and the chances of early complications like vision problems and nerve damage are high too!
Coulda, Shoulda, Woulda! You shouldn't be looking to a diabetes forum for answers for why your dad is passing out! You should be asking questions to your family physician or better yet pestering your dad to get some sort of medical help.
Unfortunately, there's not a lot we can do for you.