A big difference is that drinking soda has no effect on the person next to you. Another difference is that drinking soda occasionally likely has as much effect on your overall health as occasionally eating ice cream or a candy bar, which is to say, not that much. Another difference is that sugar and caffeine is much less of an addictive substance than nicotine.
To equate ingesting sugar with inhaling (and exhaling) carcinogens is pretty unhelpful.
Of course, there is more of a sliding scale, where a population en masse ingesting way too much sugar combined with a sedentary lifestyle can be a bigger health crisis than cigarettes, but that has much more to do with culture than the actual fact of the food itself.
According to the CDC[1] Diabetes incidence in the US has increased from roughly 2.5% to 7% since 1990.
The numbers are:
* 1980 - 2.54%
* 1990 - 2.52%
* 2000 - 4.40%
* 2010 - 6.95%
Unless legislation similar to that applied to cigarettes is introduced this train is going keep speeding further out of control. At least there are now increasing numbers of advocacy groups trying to make progress on the legislative side of things[2].
[1] https://www.cdc.gov/diabetes/statistics/slides/long_term_tre... [2] https://www.nytimes.com/2016/06/17/upshot/soda-tax-passes-in...