Your post on the Dr Pepper may not be accurate. In the US, the flavor syrup is produced under a central plant then shipped to the bottler. The bottling is done at a local facility where water and sweetner (corn syrup/sugar) is added. The can with a stamp on it are done where it hechsher is supervising the plant.

In the US, a general guideline is that since the flavor syrup is kosher (for known soda) and since the machines are “kashered” in between runs (since extreme hot water and cleaning is done to remove the syrup and sweetener between batches (for their own quality control), the bottling plants are considered acceptable.

This does not necessarily apply to fruit flavored sodas that contain grape.

As in all cases, consult your local Rav, but to be fair, without a hashgacha, the consumer may not be duped, but they do have to be continually educated.