Diet soda is out, zero sugar is in, and it's changing the soda business. Coca-Cola, PepsiCo, and Kurr Dr. . Pepper are all seeing strong growth with their zero sugar lines, even as traditional and diet sodas continue to slump.On the surface, zero sugar sodas aren't all that different from diet. Both are calorie-free and made with artificial sweeteners. But companies say the branding matters.Zero sugar resonates more with younger consumers who want to cut back on added sugar but don't connect with calorie co ...