Dan Harring (54)

This is a common occurrence, basically a cosmetic issue, and possibly the main reason the product isn’t given a longer shelf life (e.g. 2 years). The heavier-than-water insoluble material is the weighting agent ingredient, sucrose acetate isobutyrate.(SAIB). It’s meant to blend with the lighter-than-water flavor oils, so they don’t separate and end up on the surface of the sugary water solution (like cream separating from milk). The sediment is usually not visible from above, due to the curved shape of the bottle bottom.. The drink is still safe if consumed, and there’s not much reason to “shake it up” before opening. Chemical analysis with GC-MS showed virtually no breakdown of the volatile flavor compounds specific to each flavor. Formerly, brominated vegetable oil was used.; it worked better but there’s legitimate health concern about unnecessary bromine intake. Stokes Law. GC-MS Ashhurst references

Below: A somewhat long-ish read, but this is the best explanation I’ve seen of what’s going on here, particularly the “Weighting Agent” part on the second page. Click twice to enlarge. From 2nd edition of Philip Ashhurst book