Serbian prank played amongst men where one will take a dump in toilet at night and not flush leaving their pals a surprise over night to find in morning.
Andreja left a massive overnighter in sergy's toilet at his party stunk up the whole upstairs.
Either liquid niquil or any liquid drink with melatonin, Ashwaganda or other sleeping aids in a liquid form. If warm tea helps you get to sleep that could be sleepy juice too.
I could not sleep so I chugged some sleepy juice and now I'm so tired and sleepy.