IHeartRadio turns photo-sharing into a giveaway.

IHeartRadio is touring the country with a T-shirt vending machine that accepts Instagram photos as payment. The marketing effort has racked up 5.7 million impressions—likes, shares, views—in the first week on the photo-sharing app, according to iHeartRadio. The five-week campaign (which runs through Nov. 15) stops at 10 college campuses in the Midwest and South, including Arizona State University, the University of Texas and Florida State University.

“It’s a mobile-first generation that we wanted to engage with and typically you’ve got college students who are away at school, and iHeartRadio is a natural way for them to stay connected with their hometown radio station,” said Chris Williams, svp of iHeartRadio programming.

At each university, the iHeartRadio team sets up a vending machine that swaps Instagram photos for free merchandise. Passers-by first touch the screen, which then displays a unique four-digit code. Then, consumers take an Instagram picture and tag it with the hashtag #iHeartRadio followed by the code. The uploaded photo triggers the vending machine to spit out a T-shirt or a pair of sunglasses.

The company didn’t say how many campaign photos have been uploaded so far. The company initially tested the vending machines during September’s iHeartRadio Music Festival in Las Vegas.

The brand is only one of a few to test social vending machines in recent months. Old Navy, Westin Hotels and Nike have tried similar tactics, and Hot Wheels tested social commerce atthe Canadian International Auto Show last year.

“We found a way that I think was a little more novel than throwing up a pop-up tent and having a street team handing out iHeartRadio fans or something silly like that,” Williams said. “To build these Instagram vending machines and use social media as currency sends a subliminal cue about what our brand is and where we live in that ecosystem for that audience.”