There is a company whose stock has gone up 130 percent this year. It is beloved by millennials. And it’s primary product: soda water that comes in a bunch of flavors.

Rob Copeland, reporting for the Wall Street Journal, wrote about the La Croix craze. Copeland found that the combination of bright packaging and a healthy product that has no sugary additives to speak of is a winning combination right now. 

“You don’t have just one of them,” said Copeland in an interview with Marketplace host Lizzie O’Leary. “I spoke to some people who have as many as 10 a day. This is their entire water consumption.”

So everyone’s drinking it, but what actually makes it taste good? The official answer, according to Copeland, is a 100-year-old additive poetically named “essence.” But as you can see in the Wall Street Journal’s blind taste test video, it’s not always easy to identify the flavor, let alone this key ingredient.

To hear the full interview — and find out which La Croix flavor is, objectively, the best — click the audio player above.