No, it is not just the bubbles, because gingerale or sprite, etc, doesn't work. Something in COKE (pepsi works a bit, but Coke was the 'winner' in clearing feeding tubes by far.) There is something in it that helps eat away at the blockage. [note: warning for those of you who drink a lot of coke...it can/does eat away at stomach lining if too much/too if too often consumed!] Coke is definitely acidic.
Edit: They also mentioned 'cellulose' helps, too, in one of the articles. That didn't make sense to me as I thought cellulose was fiberous? And it wasn't clear if it needed to be prescribed or if it was something readily available.