The dairy industry has a familiar question for you: "Got milk?"

Six years after the popular tagline was retired, "Got milk?" ads are back. A dairy industry-funded group is reviving the campaign, hoping to prolong the boost milk has gotten during the pandemic.

U.S. milk sales have been in freefall for decades as choices grew and consumers turned to soda, juices and plant-based alternatives like soy milk. Dean Foods, the nation's biggest milk producer, filed for bankruptcy protection in November. Borden Dairy, another major producer, followed with its own bankruptcy in January.

But then came the...