Student pilot falls asleep on solo flight

When I was a Flight Instructor you will always see different habits. One of my students was extremely nervous, he kept at it. Finally he was calm and seemed more at ease when we did the incipient and full spin demonstratiom segment. Once we landed he seemed collected. In the debrief of the lesson plan I asked how he had become calm flying. He told me that he drank a six pack of beer before the lesson. He reeked of garlic so I could not detect the alcohol on him. We ceased training immediately.