The rest of the claims offered here are specious. Coca-Cola does contain small amounts of citric acid and phosphoric acid; however, all the insinuations about the dangers these acids might pose to people who drink Coca-Cola ignore a simple concept familiar to any first-year chemistry student: concentration. Coca-Cola contains less citric acid than does orange juice, and the concentration of phosphoric acid in Coke is far too small (a mere 11 to 13 grams per gallon of syrup, or about 0.20 to 0.30 per cent of the total formula) to dissolve a steak, a tooth, or a nail overnight. (Much of the item will dissolve eventually, but after a day or two you'll still have most of the tooth, a whole nail, and one very soggy T-bone.)
Besides, the gastric acid in your stomach is much stronger than any of the acids in Coca-Cola, so the Coca-Cola is harmless.