Masturbate.
Don't open your eyes afterwards.
In professional school, we used to call it 'major tranquillizer'.
Milk has morphine like substance in it.
Eating diverts blood from brain to stomach. That is why you feel drowsy after a heavy meal.
Melatonin works for a lot of people.
Alcohol makes you fall sleep but it disturbs the sleep pattern.
All 'PM's contain generic Benadryl (diphenhydramine). Don't take Tyelenol PM. You don't need Tyelenol part. The 'PM' part is generic Benadryl. Take 50 mg (two tabs/capsules). It will cause dry mouth.
All of the above (except for masturbation) are scientific facts.