Watermelon SUGA is a joke that BTS made when they were asked "What was the last song you got stuck your your head?" the began singning Watermelon Sugar High-Harry Syles. It was funny because one of the memebers stage name is "SUGA" so then they started saying. "Korean SUGA hi" "BTS SUGA hi"

(No i did not make a typo i did mean to write "Hi" because SUGA starts waving when they sing.

A euphemism for “kill me” now that composting oneself after one’s death has become popular.