NIck Jonas So Pumped Up ...

1/12/2017 7:12 AM PST

Nick Jonas As The Hulk, Not in a Movie

We'll have whatever Nick Jonas is having inside the gym -- dude walked in looking all JoBro, but walked out full Adonis.

Nick proudly showed off his ripped bod post-workout ... looking like a billboard for Jay Glazer's Unbreakable Performance Center in West Hollywood.

That hoodie had to work overtime to conceal those guns.