Check it out ... the pop star hit the stage at the Kia Forum in Los Angeles Monday evening, where she performed her new hit, "Juno" -- a song about being so into someone, you want them to make you pregnant.

Typically, Sabrina treats fans to a sexy pose while performing the NSFW anthem ... normally shouting, "Have you ever tried this one?!" to the crowd.

Yet, on Monday night, the former Disney Channel star upped the ante onstage ... as she dropped to her knees and acted out giving oral sex. She really leaned into the bit, too ... gagging on her words as she asked the concertgoers her nightly question.

Perhaps Sabrina was just feeling cheeky, as Monday night marked the final U.S. show of her "Short n' Sweet" tour.

The singer will be on break until March, when she'll hit the road in Europe ... kicking off the new leg in Dublin, Ireland.

Nonetheless, her racy movement has already sparked controversy ... with some accusing her tour of being "sex ed" and others sarcastically calling her a "great example for young fans."

However, plenty of other fans have come to Sabrina's defense ... praising the chart-topper as "hilarious."