Popular soda brand Poppi is facing a class-action lawsuit filed by a consumer who says its products don't improve gut health as much as their marketing suggests.

In a lawsuit filed last week in U.S. District Court in San Francisco, Kristin Cobbs said she purchased Poppi drinks on multiple occasions because of their labels, which say they are prebiotic sodas and feature the slogan, "Be Gut Happy. Be Gut Healthy."

But Cobbs later found that Poppi drinks contain only around 2 grams of prebiotic agave inulin fiber, which she said is insufficient to provide any real benefit. Cobbs cited research showing that consuming 7.5 grams of agave inulin daily for three weeks was insufficient to confer any meaningful prebiotic benefit.

If consumers drink more Poppi, any prebiotic benefits would be outweighed by increased sugar consumption, the lawsuit said.

Cobbs is seeking monetary relief for herself and similar customers.

Austin, Texas-based Poppi said in a statement Monday that it stands behind its products.

"We are on a mission to revolutionize soda for the next generation of soda drinkers, and we have diligently innovated to provide a tasting experience that millions of people have come to enjoy," the company said. "We believe the lawsuit is baseless, and we will vigorously defend against these allegations."

The Associated Press sent an email message seeking comment to Poppi, which is based in Austin, Texas.

Poppi is one of dozens of brands in the exploding category of functional beverages, which claim to improve health and wellness. U.S. sales of prebiotic and probiotic drinks more than tripled last year, according to data compiled by consulting firm AlixPartners.