Diet drinks have been in decline for some time now: so what are the big brands doing to improve the category's fortunes? As PepsiCo prepares to launch its reformulated aspartame-free Diet Pepsi next month, Coca-Cola and Dr Pepper have been questioned on their approach to diet drinks. In its latest quarter, The Coca-Cola Company saw 1% growth for brand Coca-Cola and 6% growth in Coca-Cola Zero worldwide, but a 7% decline in Diet Coke.