I’ve heard this theory too, and I for one am inclined to believe it. About a year ago I was in Texas visiting a friend and he introduced me to “mexican coca-cola”. Apparently coke is able to use cane sugar in the product they manufacture down there. The difference was staggering. I was immediately transported to back to the age of six . . . or the last time I’d had a “real” coke. I’ve also read about coca-cola offering “kosher coke” for passover, and some other holidays, that is sweetened with sugar instead of corn syrup . . . but I’ve yet to see it offered in my area.
The Mexican grocery stores have all sorts of wonderful things, especially if you have a sweet tooth. Try Malta or some of the other non-alcoholic malted beverages.