Drake had no choice but to cancel his Amsterdam concert because he had a prior engagement ... with a bathroom, due to extreme food poisoning.
Sources close to Drizzy tell us he ate some bad sushi on Monday, and it messed up his stomach. We're told it was so bad he had to get medical treatment immediately. It wasn't enough though ... he was still too sick to go onstage, which seriously pissed off the entire arena full of fans who'd already been waiting in their seats for 75 minutes when they got the bad news.
It was the third time in 3 months Drake had to postpone an Amsterdam gig ... which explains why fans threw crap onstage. He's promised to make up the show Wednesday.