Never accept drinks from random people you meet no matter the setting:

A 49-year-old woman has been arrested on charges of handing over drinks spiked with drugs to random high school students in Seoul after duping them into believing they were good for concentration, police said Wednesday.
At least six reports were made of students exhibiting abnormal symptoms after drinking beverages given to them by a group of people in Gangnam Ward, southern Seoul, on Monday night, according to Gangnam Police Station.
Police said the suspect, whose identity has been withheld, allegedly handed over the drinks with three other accomplices in areas where there are many private tutoring academies for students, known as hagwon.
An investigation revealed that the bottles contained methamphetamine, and false labels were attached claiming that they were intended to improve memory and concentration.
Yonhap
You can read more at the link, but it seems this group was simply trying to get these kids hooked on meth so they can keep selling it to them.