Tennis Star Amanda Anisimova's Mystery Drink Confuses Commentators During Match

Tennis pro Amanda Anisimova brewed up quite the conversation during her match against Filipino sensation Alex Eala on Monday ... when commentators debated whether she was drinking on the job.

The gulp in question went down in the second set of Anisimova's Round of 32 win at the Cincinnati Open ... and later in the showdown, Brett Haber and Lindsay Davenport dissected footage of her drinking from a clear cup amid a changeover.

The liquid looked like a beer ... as it was foamy and had the same hue as a pilsner.

"What is that, Lindsay?" Haber asked Davenport ... who replied by questioning whether it was apple cider.

"I mean, I would never suggest that a player was drinking a beer in the middle of a match, but ... that's certainly what it looked like," Haber continued.

"I mean, it could be non-alcoholic, it could be cider, it could be anything. We don't know," he added.

Well, they ended up getting to the bottom of it ... and while boozing her way to victory would've certainly been an interesting approach for Anisimova, it turns out she was just sipping a Red Bull energy drink.

"Just to put a bow on the story, we can confirm, via one of our court-side camera operators, that Anisimova asked for and was delivered a Red Bull. That is the mystery bevvy," Haber clarified.

It's not nearly as fun ... but who knows, maybe she celebrated with an actual beer after a dub over the phenom??