Coca-cola has a pH of 3.4 and in conjunction with carbon dioxide is good at dissolving metal oxides. And since one of the components is carbonic acids, it also

Coca-cola has a pH of 3.4 and in conjunction with carbon dioxide is good at dissolving metal oxides. And since one of the components is carbonic acids, it also works against lime. But then you still have to deal with the syrup residue. Fortunately, humans aren't made of metal so when you pour it into a stomach that's somewhere between 1.5 - 3.5 pH, not much happens. Except that suspended carbon dioxide is released and has to go somewhere.