I came across this interesting article on diet drinks. With the traditional model of weight control being calories in versus calories out, diet drinks are often thought of being a good substitute for sugary drinks. Sugar has widely been replaced by HFCS and artificial sweeteners in manufactured foods and drinks.
Not so! As well as being a fake food (manufactured chemical) artificial sweeteners (aspartame etc) still cause an insulin response which results in fat storage and metabolic ill heath. Read more in Jason Fungs book The Obesity Code.
So ditch the sugar altogether, including the artificial ones!
Source : Wikimedia