Cola or Pepsi?

Soda contains carbonic acid and a crapload of sugar, both of which are hell on your teeth. You could go with diet, but then you're dealing with carcinogenic artificial sweeteners. Bottled teas are a little more healthful if you get one without a lot of sugar, but they put too much ascorbic acid or phosphoric acid as preservative so as to affect the flavor.

Just drink water.