If you put sugar in granulated or powdered solid form into soda, it'll create a lot of convection points and the soda will rapidly foam up and lose a lot of its carbon dioxide.

You could use a sweet syrup instead.

This only affects sugary drinks, so their Zero and diet options should be exempt. Although a book I read recently was showing evidence that artificial sweeteners can also drive obesity, so we might start seeing things affecting those drinks too.