A tax on sugary drinks is literally a poor tax. You're taxing poor people for one of the few pleasures they have in life that they can afford easily.

You know what would improve dental health across the board? Offering free dental insurance to every man woman and child in the country. You know what would stop people from having to buy sugary drinks so often? Fully fund food stamps across the board. Give people the ability to buy healthy whole foods to feed to their kids.

Edit: My mistake in not realizing this article was about Australia. My point still stands though. A tax on sugary drinks is only going to punish poor people unnecessarily and not lead to a dramatic reduction in soft drink consumption. It was tried here in my state and failed spectacularly.