Demi Lovato: I'm Not Getting Back Together With Joe Jonas!

Demi Lovato and Joe Jonas are back together . . . on behalf of Acuvue's 1-Day Starts Today contest.

The former Disney Channel stars, who dated for several months in 2010, joined Allyson Felix, 26, Meaghan Martin, 20, and Tyler Blackburn, 25, to film promos for the brand at a private residence in Malibu on February 8. Before the shoot, Lovato, 19, denied internet reports she was rekindling the flame with her ex Jonas, 22.

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"We've been really good friends for so long. So it's been cool hanging out with him again," Lovato told Us Weekly, confirming that "nothing romantic" was happening. "I didn't even know that was a rumor!"

Lovato was excited to team up with Martin, who played her arch nemesis in the Camp Rock movies. "It's cool because we've gotten to work together before, and now we're working together again. It's kind of like a reunion," she said. "So it's nice. It's really fun."

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Jonas added: "I've been lucky to be able to work with a lot of great people in my life, two of whom are Demi and Meaghan. . . It's been a while since I've seen them."

"We've all been kind of on different paths, but I see them at award shows and things like that," Jonas told Us. "And any time we see them, it's like family reunion. We have catch-up time and reminisce."

The five stars will mentor the winners of Acuvue's 1-Day Starts Today contest, which asks users to upload a one-minute YouTube video revealing their secret hopes and dreams. "I've never really mentored anybody before other than like my little sister, so it's going to be exciting," Lovato said.

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Pretty Little Liars star Blackburn added: "It's exciting that I'm going to be able to see somebody experience a taste of what they want to do with their lives. . . if I was 15 or 16 and that happened to me, I would be beside myself. The fact that I can actual lend a hand [in making someone's dream come true] is so fun."

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