[xaa]

How about the following:

1. Find a substance that is chemically tooth-like

2. Split it into predefined volumes (little cubes or spheres)

3. Add the beverage and saliva to the "tooth", wait a month, and measure the decrease in "tooth" volume.

4. Use regression to estimate the coefficients for sugar, pH, and whatever else.

[lotsofpulp]

You would be missing the bacteria, which are essential.