A large amount of food consumption is impulsive and socially mediated. Lunches may be time limited but are generally social events with co-workers or social acquaintances. Dinners are frequently social events. In these settings 'cost' is rather low on the list of decision-making criteria. Even if browsing a bookstore while alone, a "coffee break" will focus on a gourmet blend and some sugary snack. The added sugar-tax burden will have virtually no effect on any decision making in such situations. It would take a dedication to sugar-avoidance and this is not likely to be instilled in someone by slightly higher prices.
Hello FleaStiff, very good points and I agree with them. Best wishes, Robert