Of interest:

The Role of Vitamin C in Two Distinct Physiological States: Physical Activity and Sleep, Nutrients, December 2020

Our work has led us to the conclusion that supplementation with vitamin C has a contradictory effect on sleep quality and physical activity. By increasing the consumption of this antioxidant, one can potentially help increase sleep duration, reduce sleep disturbances, relieve movement disorders, and decrease the dangerous effects of sleep apnea. On the other hand, caution is needed when using this vitamin as a supplement during physical training. No improvement, or sometimes even deterioration of physical performance, undesirable metabolic changes in the blood and muscles, and decline in antioxidant activity were often observed, especially when high levels of vitamin C were administered.

I knew that vitamin C interfered with exercise (Vitamin C Supplements Reduce Endurance, Fatigue Muscles Sooner). I didn’t know that it could improve sleep.

So, there’s an optimum intake range for vitamin C. A gram or more is probably too much. But several hundred milligrams (RDA is give-or-take 100 mg) may improve sleep. (Dr. Greger of NutritionFacts likes 200 mg/day.)