WHAT CAUSES CRAVINGS FOR CARBONATED DRNKS?

All food and drink are addictive.

That's why there is such an obesity problem in many lands of plenty.

I would not have thought that carbonated drinks are anything special
except to the extent that they are made to seem 'cool' by clever
promotions.

Many carbonated drinks are very high in sugar. So the craving could be
a need for a sugar hit.

Here's a likely suspect: caffeine.
read about caffeine here: http://home.howstuffworks.com/caffeine.htm

The combination of caffeine, simple sugars and CO2 is readily absorbed
by the digestive tract, perhaps more so than simple coffee. Generally
speaking one should
keep caffeine consumption to <200mg/day to avoid possible anxiety
disorders and consume complex carbohydrates instead of simple ones
(glucose/sugar) to reduce sudden blood glucose peaks (makes you fat
and makes you crave glucose again).