What Can Cause Dizziness, Fainting And Fatigue Episode Abruptly?

My friend, male 47 is a chronic alcoholic, suffers sleep disorder (deprivation), and barely eats. He did not drink yesterday but could not sleep. Got up at 5:30, drank a pot of coffee and went to work at 8 AM. He worked very hard physically at a new job this morning and felt dizzy. He sat down, expecting the dizziness to pass but saw flashing lights, and then red lights and passed out. He bit his tongue hard and it is swollen. The owner of the home he was working at found him passed out on her lawn and called the ambulance. He would not go to the hospital. He slept from 3 PM to just now and is feeling very tired. He will not go to the hospital. Is this a stroke or alcohol withdrawal seizure? I have counselled him to go to hospital but he won t.