The singer had a tough time hiding her frustration during segment centered around drinking during the season finale of The X Factor on Thursday, Dec. 19.
"All season long, Simon [Cowell] has complained about Demi being annoying," host Mario Lopez said. "Maybe it has something to do with what she's been drinking at the judge's desk. Let's take a look."
The clip featured several digitally altered scenes showing Lovato consuming a mysterious green substance, which was revealed to be "annoying juice."
But the 21-year-old did not think the drinking joke was funny and was seen mouthing "that was f--ked up" as the clip played.
"Well I think that it's very, very clear, since I don't drink anymore, 'annoying juice' has become my new drink," Lovato responded as she tried to conceal her anger with a forced smile. "I love it because I get to annoy Simon with it," she added as she high-fived fellow judge Paulina Rubio.
You tell 'em, Demi.
Lovato confirmed that she would not be returning to the singing competition series next season, saying "I started the show being a singer and a musician, and so I'm going to go back to that. It's been really great, but I'm so excited for 2014. I'm going to dedicate it completely and entirely to music—touring and making a new album. Possibly releasing one."
Boyfriend-girlfriend duo Alex and Sierra are the newest champions of The X Factor, winning the coveted $1 million prize and a record contract with Sony.