I don't know. I heard the same story except it wasn't for insect control, it was the sugars and phosphoric acid.

If "colas" do kill insects, I've not seen anything that supports this yet, think what they would do to you or those who do drink "colas". There were, unsupported, allegations circulating around India several years ago that both of the major cola companies were 1) using water laced with pesticides, 2) adding pesticides to their products sold in India which the companies of course denied and which no one could confirm. There was also a story from England that some orange soda contained (a research lab supposedly confirmned this) pesticides. Much of this "information" has been circulating via EMails and according to the Snopes and Urban Legends web sites state these are hoaxes.

Colas bring phosphorous and carbohydrates to the plant surfaces. We have an organic radio show on Saturday and Sunday in San Antonio. The guy regularly recommends sprays with liquid seaweed for control of spider mites and other sucking insects. Sometimes he recommends adding a little molasses to the spray. I believe the idea is to feed the microbes that live on the plants. Those microbes, like soil microbes, will help the plant to fight off pests if they are well fed.

I judged high school science fairs for 20 years. The idea of applying certain chemical gasses is very well known to high schoolers. I'm not sure where they learned it, but the results I saw over the years were pretty convincing. One of the gasses used all the time is from oil of wintergreen. Interestingly it is almost the same chemical formula as aspirin.