Having read quite a few of the prospective studies, there are usually considerable and sometimes fairly comprehensive attempts to statistically correct for other background and lifestyle factors.

For example, this study on Tehranian children and teens adjusted for age, sex, total energy intake, physical activity, family history of diabetes, intakes of dietary fiber, tea and coffee, red and processed meat, fruits and vegetables and BMI. This one on Taiwanese teens adjusted for Taiwanese region, age, physical activity, total calories, the intake of meat, fruit, fried food, food with jelly/honey, alcohol drinking and cigarette smoking. This one in Korean adults adjusted for adjusted for age, energy intake, household income, education level, alcohol consumption, smoking status, and physical activity.

It's obviously impossible to prove causality with prospective epidemiology. But when there the mass of benchtop, animal, case control and prospective studies pointing to the same conclusion, at some point its time to stop shilling for Coca-cola.