Joe also revealed who his favorite kisser is.
The Internet loves to gush over Joe and Nick Jonas' incredible abs, but according to Joe, the title of "Hottest Jonas Brother" belongs to someone else.
"Frankie [is the hottest one]," Jonas told ET's Denny Directo at DNCE's Musical.ly Muser Mingle in Los Angeles on Thursday.
EXCLUSIVE: Nick Jonas Weighs In on Who’s the Hotter Jonas Brother -- Him or Joe?
All jokes aside, Joe and Nick have been hitting the gym hard.
"I think for both of us, we obviously like to train, but when we're in the gym together, it's just a different thing," Joe said. "We have favorites we like to do and every once in awhile we'll try to bump it up and go at it."
Joe doesn't just have moves in the gym. He also puts the moves on Nicki Minaj in the music video for DNCE's new single, "Kissing Strangers," though he says the two didn't actually kiss.
"Obviously we like to tease people, and that's part of the fun," he confessed. "[But] we'll have some performance live, so we'll see."
WATCH: Nicki Minaj and Joe Jonas Get Steamy in New 'Kissing Strangers' Music Video
In the meantime, ET played a little game of "kiss and tell" with the band, who are challenging fans to kiss some strangers of their own by sharing their own music videos to "Kissing Strangers" on the Musical.ly app.
One word to describe Joe's first kiss?
"Bowling alley," he said, while bandmate Jack Lawless called his "embarrassing."
Joe's favorite kissing tip is "gum," but his favorite kisser surprisingly isn't girlfriend Sophie Turner -- it's cleverly "the band Kiss."
As for a famous stranger he'd like to kiss, that would be Naomi Campbell.
"Penelope Cruz and me have some unfinished business," Cole Whittle revealed, while JinJoo Lee confessed she'd like to lock lips with Daniel Craig.
"She stole my answer," Lawless joked.
DNCE's hashtag challenge #KissingStrangers is now live on the Musical.ly app, where fans can submit their own videos of the song using the hashtag.
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