Dirty soda shops got TikTok famous. Can they outlive the trend cycle?

Two years ago, franchise soda shops were a Utah anomaly. Now, thanks to some viral TikToks and a Hulu reality show, the shops have exploded nationwide.  Franchisees and entrepreneurs are betting big on the “dirty soda” shop concept, which offers customers the opportunity to customize their drinks with syrups and creamers. These shops benefited from a September sales bump with The Secret Lives of Mormon Wives, a reality TV hit where the “Wives” continually lugged around 32-ounce...