1. Set your alarm for 1-2 hours before you actually need to wake up.
2. When the alarm goes off, take 1-2 Ibuprofen, drink some water, reset your alarm, and go back to sleep.
3. Wake up at the scheduled time, hangover free.
Note: Don't abuse this technique, as it will take a toll on your kidneys and can be hard on your stomach lining. But in a pinch, it straight up works.
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Edit: I just went and looked up the side effects of ibuprofen on the stomach lining and all I have to say is, "Holy crap!". This would explain why I have been having to take anti-acid medicine for years! The ibuprofen bottle doesn't even mention the risks to your stomach, and my doctors and gastroenterologist never said anything about it either. They just blamed it on my weight.