When it comes down to it, the main thing you want to try to control is the pH in your mouth. You may or may not remember much from chemistry class, but acidic substances have a pH less than 7 and basic (or alkaline) substances have a pH greater than 7. Water has a pH very close to 7, or neutral.

Two things to remember:
1. Acid weakens or de-mineralizes enamel.
2. Takes almost an hour for your mouth to return to normal pH.

Therefore, it would be better for your teeth if you drink three cans of soda in a short amount of time instead of sipping on one can over several hours. Frequency is more important than quantity.