With a little more than four minutes remaining in the third quarter and Sacramento leading 64-62, Kanter received an entry pass in the paint from Dante Exum. Surrounded by two defenders, Kanter shuffled his feet as he tried to find an open look at the hoop, and he was subsequently whistled for traveling.
Following the call, Kanter slammed the ball to the court in frustration and whipped his mouthguard into the stands behind Utah's bench. He was assessed a technical foul for that action but was not ejected.
Somewhat humorously, a "lucky" fan collected Kanter's mouthguard as a souvenir.
Kanter, 22, is earning $5.7 million in the fourth year of his rookie contract this season. He issued an apology for throwing his mouthpiece on Tuesday.
"I sincerely [apologize to] Sacramento fans and the NBA for last night's incident," he wrote. "[I] never [intended to] aim [or] to throw [it] anyone. It was just out of frustration and [I] fully take responsibility. [It will] never occur again."
The $25,000 fine for the mouthguard toss is consistent with previous discipline from the league office. Then-Kings guard Aaron Brooks was fined the same amount for throwing his mouthpiece into the stands in Nov. 2012. Raptors forward Amir Johnson was also suspended for one game without pay in Dec. 2012 when he threw his mouthguard at an official following an ejection.