Sydney Sweeney Sings Breakup Anthem at Karaoke Amid Jonathan Davino Split

Sydney Sweeney's singing those breakup blues away -- she let loose at a karaoke bar in Key West, Florida last night while taking on Adele's breakup anthem, "Someone Like You."

We've got video of Sydney's late-night escapades at Key West's Backyard Bar Wednesday ... and she was having the time of her life, belting out the recognizable tune with some pals -- although it's unclear if they're her pals or some of the locals an eyewitness said she hopped onstage with.

Sydney clearly didn't want the night to end as she warned the DJ she's staying there "forever" ... playfully adding, "Don't get tired of me!"

The blonde bombshell is no stranger to the karaoke stage. In fact, we have footage of her taking over the stage in April '24 as well, with her "Anyone But You" costar Hadley Robinson.

The biggest difference between the videos? Her relationship status.

As we reported ... Sydney and her former fiancé Jonathan Davino have been living separate lives since January -- though they were spotted trying to lay low for a lunchtime rendezvous earlier this month.