The whole "Our soda taste so much better than the unnamed competitor's!" style advertising would quickly change to something like "X Corp Brand Soda is the biggest supporter of elephant extermination worldwide and uses lead to give their product their sugar-free sweetness. Is their soda really worth it? (haha, just kidding. Or are we?)"

Smaller companies would be absolutely crushed by larger corporations dragging them through the mud with political style ads all day.