Come Passover, all Coke in the stores is cane sugar (so I'm told). I don't drink much Coke, and if you put two glasses in front of me, I'm pretty confident that I could tell you whether they're the same sweetener or different. I'll notice the switch at the beginning and end of Passover. Since I'm not Jewish, and since Passover moves around, I'll claim this is close enough to a blind test.

For my money the elusive perfect Coke comes from a soda fountain that's adjusted just so. Couldn't tell you what's different, but some just nail the perfect carbonation level and syrup ratio. When I find one, I usually have three or four in rapturous joy, because it'll be months before I find one again.