Poppi, a prebiotic soda brand, is changing the beverage industry by proving that functional drinks can succeed where many have failed. For a long time, investors have been wary of beverage startups, worrying that low profits and tough distribution challenges would prevent them from thriving. However, Poppi's story shows that there is a new wave of "functional soda" companies that are overturning these doubts and making an impact.

Founded by a passionate entrepreneur, Poppi started as a simple i...