Giving the semiconscious person food could cause vomiting, choking, or aspiration. If you cannot keep the person awake, position them on their side in a fetal position . Place a pillow in the small of their back to prevent them from rolling out of this position. This is important to help prevent aspiration if the person should vomit. Just because the person is sleeping doesn't mean that the alcohol cannot get to the brain.
Alcohol levels continue to rise, causing the person to become unconscious, rather than asleep.
If at any time you can not wake the person up, CALL 911 . This is a medical emergency and you MUST get help.