I don't know your lesson, but I can give my own argument, hopefully it will help!
One of the main arguments concerning the ban on the soda drinks is that those are often drank without the real understanding of their effect on health. Because they are liquids many people might be mistaken to think they are not as unhealthy as foods. Therefore they might not have any inhibition to buy it. Soda ban would force the shops to provide alternatives to those drinks. As a result, the people might choose to buy healthier drinks without even realizing it.