The New Coke campaign of the early 80's was considered one of the biggest marketing failures ever. Well, it's not. It is in fact one of the most brilliant and immoral marketing strategies in history. This is all true, just look on any can of Coke.
In the 1980's when Bill Cosby declared that Coke would change its formula, it was a huge scam to save Coke money. You see, the Coca-Cola corporation never dreamed that people would like New Coke. What they wanted was to release a substitute Coke product with a noticeably different taste. They would keep this on the market until all of the old Coke was sold and people couldn't get it anymore.
Eventually, Coke co. claimed (quite rightly) that people missed old Coke and demanded its return. As a consequence, Coke vowed to rerelease the original Coke as Coke Classic. They never did. What they did do was bring back the original recipe, but with (significantly cheaper) corn syrup instead of sugar.
Everyone would have noticed if they had just made the switch directly. Coke would have been forced to return to the original, more expensive, product. But since Classic Coke tasted passably similar to old Coke, people just assumed it was the same, since no one had had any in so long.
So now you can only get original Coke in the US on Passover (look for Kosher for Passover Coke from about mid March, it will either say KP, or just look for Hebrew letters). Since corn is not kosher for Passover, they release the true original formula with sugar.
In Europe, Coke is still made with real sugar.