There is an interesting paper in Nutrition Research "Acidic Beverages Increase the Risk of in vitro Tooth Erosion". A group at U of Iowa College of Dentistry compared the effect of Gatorade, Red Bull, Coke, Diet Coke, and Apple Juice, as examples of sports drinks, energy drinks, carbonated soft drinks, diet drinks and juices, respectively, on extracted teeth.
In a pretty simple setup, they simply soaked the extracted teeth in each drink for 25 hours, refreshing the liquid every 5 hours. The acidities of the drinks were measured by straight forward titration. They only went high-tech, and thus beyond what you could do in a high school chemistry class, when they started to measuring the lesions.
Interestingly, the lesion depths corresponded roughly but not exactly with the acidity of the drinks. The most acidic drink was Red Bull, but Gatorade did the most harm. The lesions were measured in micrometers and the results were Gatorade (131), Red Bull (100), Coke (92), Diet Coke (61) and 100% Apple Juice (57).
Anyone who has seen the chemistry demonstration in which a highly acidic solution is used to dissolve a tooth, will not be surprised. This study appears to be a more scientific recreation of the same thing. It still does not tell you exactly what is going to happen under in vivo conditions, but basic chemistry suggests that anyone who spends a great deal of time each day swishing around acidic liquids is not doing his or her teeth much good.
If you want the opposite effect, try dairy. There appear to be a number of reasons why dairy actually acts to inhibit tooth decay (calcium, active proteins, beneficial bacteria, low acidity, etc.). Below are two representative papers on dairy and dental health.