Am reading Clapton’s bio. He and Lennon snorted to much coke before a Plastic Band concert in Toronto. Lennon puked his guts out. I guess I didn’t realize that Justin is as pure as the driven snow!
Justin Bieber isn’t Clapton or Lennon and you projecting their problems on another generational star is your problem - and says far more about you than Beiber.
As was said up thread, too much milk before singing can cause vomiting. I also know this from experience with my daughter. Dairy products coat the vocal cords and make singing difficult, one of the ways they deal with it is lemon juice to the back of the throat. Lemon juice on top of a large quantity of milk is going to cause a reaction in the stomach - which ain’t pretty.