There are a number of small, independent Coca-Cola bottlers out there that use only 100% cane sugar. There is an entire network of Coke freaks who eschew any other sweetening and have websites dedicated to the preservation of their beverage. You can Google around a bit and turn this information (and gallons more) up.
One such independent bottler that operates on a large scale is in the Missouri/Kansas/Oklahoma/Arkansas area: Ozarks Coca-Cola, with headquarters in Springfield, Missouri. This sizeable company may or may not use only cane sugar, but an e-mail to them might turn you up one of the remaining 75 other independent bottlers in one's home turf that still do so.
The last time I knew, Double Cola in Chattanooga only used cane sugar; a large portion of their output is now sold overseas. If you want Double-Cola around here, you have to go to places like Cleveland, Tennessee or Dalton, Georgia to find it... many stores in Chattanooga have stopped carrying it, for some inexplicable reason. Double Cola is also a strong seller in both Huntsville, Alabama and Evansville, Indiana.
Hope this is of at least some help.
Carbonated And Carbondated, Ort. Carlton in Fizzy, Effervescent Athens, Georgia.
P. S. Since I am hypoglycaemic, I can only drink the diet versions... and I can attest that Diet Double Cola is mighty good.