What does coke eat away at?

The fizzy drink Cola is high in sugar and therefore is more likely to cause tooth loss through decay.

This isn't the Coke's fault but the bacteria in your mouth that uses the sugar for food. When they eat sugar from any source, they excrete acids which erodes the surface of the tooth. Once the hard outer layer is broken through, the tooth contains pulp which is soft and easily infected by other bacteria's and microbes. It is these which eat the lining and nerve of the tooth causing it to abbess and potentially fall out if not repaired by a dentist.

All those scare videos on YouTube where you see a penny made bright by Coke is actually caused by the dissolved carbon-dioxide lifting the oxidised layer off the penny, and not the action of acids in the coke.

Any carbonated drink even soda water (which is just bubbly water with no ingredients) will do the same thing.