Oats, eggs and fish. Also among nuts, pistachios have the highest amount of melatonin. If you’re looking for fruits sour cherries are a pretty good source of melatonin as well. But you’ll have to eat a lot of these to get a full effect as compared to getting the melatonin from a supplement. I would personally reccomend melatonin gummies, can’t go wrong with those, they are much more concentrated.
Even on good nights of sleep,the brain produces <.2mg of melatonin and that’s all you need to have a good nights sleep. Exogenous consumption of melatonin will destroy your ability to produce endogenous melatonin.