Obviously there are many things going on here, and I am not saying this is the end all explanation to the whole thing, but an interesting part of the puzzle I came across during a project I did on the brewery industry during my bachelor, is that there exists a whole market segment of consumers who just wants to "try something new".

When you ask yourself in the super market "Who in their right mind wants a snickers and mint flavored orea?" this is that segment.

So, in my case, the beer industry was (is? This was a decade ago) losing sales to ready-mades (Barcadi Breezer, cans of rum and coke, etc.) and a way to hold on to consumers was simply to add new, limited run recipes.

All classes of drinks are trying to hold on to consumers who are being stolen by other classes of drinks, by offering up new colors and strange flavor combinations.

But at the same time I think you are right about companies training consumers to drink larger and larger portions sugared drinks. Like, 1.5 liter coca-cola isn't even the largest size drink in the cinema sometimes!