@Ghlighte that's actually a great idea! i can actually just make the particle emmiter invisible so just the particles remain so there's no problem with having the same properties as the cola, i'll see what i can do when i get home, thanks!
@hideki see what works best. Simple bubbles with default glass material and non-inverted normals will probably do just fine, but will look like tiny glass beads if you make a close-up shot of the glass. And inverting normals and matching the material is free in terms of render times. As an alternative to inverting normals, you can set the IOR to 1/(IOR of cola), the results will be identical.