New York CNN Business  — 

Burger King wants people to download its app. So it’s sending them to McDonald’s for access to a one-cent Whopper.

Here’s how it works: If you’re within 600-feet of a McDonald’s you can unlock a deal for a penny Whopper using the Burger King app. The app then offers directions to a nearby participating Burger King, where you can pick up the burger. The company announced the deal on Tuesday. It runs through December 12, and customers can only access it once.

Burger King’s not the only fast food chain trying out creative ways to get people to download its mobile app. McDonald’s recently ran a $1 fries promotion through its app, and Wendy’s often offers deals through its app as well. Through digital platforms, fast food chains can learn more about consumer tastes and offer personalized promotions.

Fast food chains use stunts to get customers to pay attention, and vie for their business. Fast food eaters aren’t particularly loyal to one brand over another, BTIG analyst Peter Saleh told CNN Business this summer.

For Burger King, its particularly important to win back customers.

The burger chain only recently announced plans to upgrade its stores to include digital menu boards and self-order kiosks — changes that its rivals have already put into place, helping increase sales.

Burger King’s US comparable sales slipped by 0.7% in the third quarter. Meanwhile, same-store US sales rose by 2.4% in the third quarter at McDonald’s.

Still, Burger King’s cheeky approach is “pretty innovative,” noted Morningstar analyst R.J. Hottovy. And so far, it’s been a huge success.

More than 50,000 people have redeemed the deal so far, Burger King’s Global Chief Marketing Officer Fernando Machado told CNN Business. That’s about 20 times more redemptions than for any other Burger King app promotion, he estimated.

The promotion also boosted the app from ninth to first place in the iTunes App Store’s food and drink category, he said.

To pull the Whopper Detour off, Burger King geofenced more than 14,000 US McDonald’s locations. Machado said that it took about a year to pull the promotion together. “We want the functionality to be working really well,” he said. “Or else it backfires.”

Some people have complained about glitches on Twitter. Machado’s not too worried about that.

“Sometimes someone has a poor connection, or maybe one specific restaurant out of 14,000 may not have been geolocated properly or somebody tried to redeem the coupon during breakfast,” Machado said. But he noted that the difficulties have been the “exception.”

The fast food brand has a history of flashy stunts. In January, the chain released an ad criticizing the Trump administration’s decision to repeal net neutrality rules. The three-minute ad shows a “social experiment” in which a Burger King store implements a Whopper “fast lane.”

It also released a video showing employees charging female customers a “chick tax” on chicken fries in pink packaging for a stunt designed to call attention to the so-called pink tax on women’s products.

To promote the Whopper Detour, Burger King published a video showing customers ordering Whoppers from confused McDonald’s employees.

Machado doesn’t recommend that people go through McDonald’s drive-thrus to redeem their burgers.

“We don’t want to disrupt,” he said, noting that one of the reasons the chain settled on a 600-foot radius was to make sure people didn’t have to use the drive-thru to access the promotion.

Burger King’s strategy is a bit risky, Hottovy noted. Not only does the tech have to work well, but once Burger King has driven customers to McDonald’s, they may just order food from McDonald’s.

“Convenience is really what consumer are looking for,” he noted. That “may even trump free food giveaways.”

Burger King didn’t let McDonald’s know what was coming. “We forgot to tell them,” Machado said, adding that McDonald’s hasn’t reached out, but that he hopes the rival sees the stunt as just a bit of fun.

McDonald’s did not respond to a request for comment.

It’s not unusual for fast food rivals to go after McDonald’s (MCD) in their marketing, Hottovy said. “McDonald’s is the largest player in this category,” he noted. That puts “a target on their back.”