To combat jet lag, or otherwise reset your sleep schedule if it has drifted...
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Go 24 hours without eating.
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Go to bed early enough to make sure you get 8-10 hours before you normally want to wake up.
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Using an alarm, wake up a bit earlier than you usually want to wake up.
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Make a big breakfast, eating when you normally want to wake up.
Now your body will have reset its circadian rhythm, and you'll naturally wake up at that time.
Practice, I guess?