I've switched to ginger ale (no caffeine but still full of sugar) and haven't noticed any ill effects of being decaffeinated. I can still wake up at the crack of dawn, and aside from that day earlier this week where I got no more than about five hours of sleep, haven't felt tired during the day at all.
I read that the US per-capita annual consumption of Coke in servings is 411. A can of Coke is 12 oz, so I'm not sure whether a can is one serving or 1.5 (if they're measuring by 8 oz serving). In any case, that's one heck of a lot of sugar and caffeine.
Years ago I completely eliminated aspartame from my diet; I'm considering doing the same with caffeine. I still enjoy tea, but fortunately there are caffeine-free (or low-caffeine) options such as herbal or white teas.