Remember those old commercials where a guy had to take a swig from two unlabeled drinks and guess whether his favorite one was Pepsi or Coke? They’re probably the most famous example of a blind taste test, and they were Pepsi’s attempt to prove that more Americans actually preferred its beverage.

Now Burger King is trying something similar. In a clever marketing campaign, it’s daring its customers in Sweden to order off a new “50/50 menu.” Ask for a burger and you’ll be handed either a patty made of real meat or a plant-based patty. The restaurant won’t tell you which it is — you have to guess.

Only once you’ve guessed do you get the opportunity to scan a code on your box using the Burger King smartphone app and find out what your burger was made of. The idea is to show customers that they can’t tell the difference between the two patties, so they might as well go for the one that’s kinder to animals and the environment.

The rise of meat alternatives could help save hundreds of thousands of animals from suffering on factory farms, and it could fight global warming by reducing the number of methane-producing cattle. It could also combat other problems like antibiotic resistance.

To promote the 50/50 challenge, Burger King has released a commercial in which one woman calls the meatless burger “a bloody mindfuck!” It’s hard to imagine this ad making it onto the airwaves in the US, but it’s a pretty ingenious piece of marketing — as is the decision to dub the new mock-beef and mock-chicken products “Rebel Whoppers” and “Rebel Chicken King burgers.”

“We are really proud of how hard it is to tell our plant-based burgers apart from real meat. With the 50/50 menu, we hope that more people dare to try them. And hopefully have fun trying to figure out which one they got,” Daniel Schröder, the marketing director for Burger King Sweden, said in a statement.

It’s more than just fun, mind you — it’s also a data-gathering experiment. Burger King is collecting customers’ guesses and plans to release the data in a new wave of commercials that’ll run later this summer in Sweden.

Will the blind taste test, meatless meat edition, make its way to the US soon? So far, there’s no indication of that. Nevertheless, every Burger King in the country will offer meatless Whoppers by the end of the year, according to the fast-food chain.

In the US, the meatless burger is a partnership with the startup Impossible Foods, which supplies patties made with heme, a protein cultivated from soybean roots that mimics the texture of meat. It even “bleeds,” just like real beef.

Burger King started its American foray into meatless meat by giving the Impossible Whopper a trial run in 59 restaurants in the St. Louis area — and found that those locations enjoyed 18 percent higher foot traffic than the chain’s national average. Encouraged by the results, the chain quickly announced it would make the product available in all 7,200 branches nationwide. For now, you can find them in Missouri, Florida, Georgia, Alabama, and 111 restaurants in the greater San Francisco Bay Area.

In Sweden, Burger King’s new meatless products are apparently not coming from Impossible Foods. That company’s method for making the key ingredient, heme, involves genetic modification and would need to be approved by European authorities. The Rebel Whoppers and Rebel Chicken King burgers are created using different ingredients. As the Spoon reports:

The chain has been tight-lipped about where they’re sourcing their new vegetarian options. Over email, BK Sweden’s General Manager Iwo Zakowski would only reveal that the producer of the plant-based chicken and burger patty were based in Europe. So, not Impossible.

The sourcing may be murky, but it’s clear these products are part of a trend that goes way beyond Burger King. The past few months have been a time of incredible growth for the alternative meat movement, and as consumer demand surges, investors have been jumping on board. In May, Impossible Foods raised $300 million in new investor funding. Its rival, Beyond Meat, went public and its stock jumped from $25 to $80.

In April, Del Taco announced it’s partnering with Beyond Meat to offer new meatless tacos, and Qdoba announced that all 730 of its locations will offer Impossible Foods’ meat alternative.

These companies were following in the footsteps of early adopters like White Castle, which sells a slider version of the patty produced by Impossible Foods, and Carl’s Jr., which offers a veggie burger made by Beyond Meat.

By now, it’s obvious there is profit to be made in the plant-based meat business. But consumer doubt is an enduring problem: Some people still don’t believe that a meatless burger can ever truly replace the real thing.

That’s why a blind taste test like the one Burger King is now running in Sweden is important. If it can prove to the doubters that even they can’t tell the difference, it stands to substantially advance the meatless meat movement.

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