Cavs Fill Rookie's Car W/ Popcorn, Donovan Mitchell Foreshadows During Game

Cavs rookie Jaylon Tyson learned the hard way to NEVER forget the doughnuts -- 'cause the young hooper got a car full of popcorn after Cleveland's win over the Brooklyn Nets ... and he should've seen it coming after some solid foreshadowing from Donovan Mitchell.

Spida -- who sat out of Tuesday's contest as he deals with a groin injury -- documented the postgame hijinks on his Instagram ... showing the 22-year-old Cal product walking up to his whip as his teammates playfully scolded him for not providing pastries for them to enjoy.

Once Tyson opened his door, he knew just how big of a mistake he made ... discovering a bunch of popped kernels throughout his car's interior.

As it turns out, Mitchell warned Tyson during the 109-104 victory ... as he was spotted chowing down on some popcorn while supporting his team from the bench.

Mitchell seemed to regret having to waste so much of the snack ... 'cause he admitted "that s*** good, too" as Tyson surveyed the damage.

The Cavs are clearly gelling on and off the court -- they have the best record in the league and are currently on a 15-game winning streak.

They've secured a division championship already ... so they can now shift their focus to a playoff run.