Cereal and Milk
The right combination of carbs and protein helps produce serotonin— helping produce melatonin— which has a calming effect on the body and mind. Be sure to stay away from the sugary types of cereals, though.
Bananas contain magnesium, which acts as a natural muscle relaxant.
If you can find it, buy it! Passionfruit contains somniferum, which contains sleep-inducing properties. Eat as is, or as a juice/tea.
A 2011 study published in the European Journal of Nutrition found that tart cherry juice is a great sleep aid. Adults who drank two glasses of cherry juice daily slept an average of 39 minutes longer than usual. Try adding 1 cup into a smoothie!