1. Crackers and bread. The simple starches turns to sugar really fast. And they get stuck in your teeth, so the bacteria has even more time to turn that sugar into acid.
2. Dried fruit. It's as bad as candy because it basically IS candy. And it's stickier than most candy is, so it stays on your teeth longer.
3. Grapefruit. There's sugar in it, and it's naturally very acidic. Lemons, limes, cranberries, and grapes are really acidic too. Oranges actually aren't as bad.
4. Coffee. It has a lot of acid and stains your teeth.
5. Diet soda. It's worse than regular soda, because they add phosphoric acid to make it tangy. So even without sugar, there's more acid to rip up your enamel.