A self-proclaimed biohacker, Dave Asprey, claims that waking up between 3-5 am and struggling to fall back asleep is often due to a blood sugar crash. According to him, the body releases stress hormones cortisol and adrenaline during this time, causing wakefulness. To combat this, he suggests having a snack before bed, such as raw honey, collagen, or MCT oil.

Source: https://www.wionews.com/entertainment/lifestyle/news-reason-why-some-people-wake-up-between-3-5-am-and-cant-go-back-to-sleep-as-per-a-biohacker-773115