Side effects on teeth of drinking 24 oz of coke a day throughout 20s?

Not ideal...: Soda damages teeth in two ways. First, the bacteria in your mouth use this as a very rich sugar source and their breakdown products cause cavities. Second, the acid from the drinks softens and breaks down the enamel on your teeth. Frequency is the big thing here. If you're going to drink a can of soda, have it with a meal. Don't sip on it thoughout the day...That's about the worst thing you can do.

Decay Possibly: Coke, a carbonated drink with a generous amount of sugar can play a role in dental disease. Decay requires three factors to be present to occur. 1) teeth 2) bacteria 3) sugar. The bacteria colonize on your teeth, form plaque, eat the sugar and produce acid. The acid demineralizes the tooth to form holes called cavities. If you eliminate the bacteria with brushing/flossing you minimise the risk.