What's wrong with dark soda?!
Imagine all the ingredients that are in sodas, I only trust pure spring waters
No soda is really 'good' but people might say that dark sodas are bad because they do have a high concentration of sugars, syrups, and dyes than, say, a Sprite would.
I think it is because of the caffeine in dark sodas. Caffeine makes it harder for your kidneys to produce urine.