Klaasen hit the next ball for four, but after that there was a stoppage when the object was hurled at Super Giants batter Prerak Mankad, according to Jonty Rhodes.
Rhodes, the Super Giants fielding coach, tweeted that the object hit Mankad on the head while he was fielding at long-on, close to the Super Giants dugout.
Speaking to the broadcaster after the innings, Klaasen said that the episode broke the Sunrisers batters' momentum, and added his criticism of the umpiring.
"Disappointed with the crowd. That's not what you want from a crowd. It broke a lot of momentum," Klaasen said. "Hopefully the umpires stay consistent. Not great umpiring."
He was later fined 10% of his match fees for breaching the IPL code of conduct. The official IPL statement didn't specify the reason for the penalty, only saying, "Klaasen admitted to the Level 1 Offence under Article 2.7 which states the use of public criticism/inappropriate comment in the IPL's Code of Conduct."
Klaasen scored 47 to help Sunrisers reach 182 after opting to bat. But a half-century from Mankad and explosive knocks from Marcus Stoinis and Nicholas Pooran helped Super Giants win the game in the last over.