Sleepy girl mocktail is a viral 2023 TikTok drink combining tart cherry juice, magnesium powder, and prebiotic soda, marketed for sleep. Not particularly concerning, generally safe ingredients; magnesium can interact with some medications. If your kid uses it constantly, ask them where they first heard it, not to police their speech but to understand which online community they are in. Most slang of this kind moves through TikTok and group chats, so seeing it in your child's vocabulary just means they are plugged into normal teen internet culture.