Feeling energized for eight straight hours not a very good, and few people can do that consistantly without some sort of stimulant. Like Keith said, are you sure your caffeine habit isn't masking other energy-related problems like inconsistant sleep schedule and unhealthy diet?
Make a bet, or start a betting pool with your co-workers about whether you can quit or not. Or tell your coworkers that you'll pay them 100 dollars if they catch you drinking pop like that. Not willing to?
That's essentially negative punishment, but you can also do some positive reinforcement. Every time you drink a bottle (or cup or whatever) of water or juice, reward yourself.
You might also want to put lots of water and juice (cold, if possible, maybe in a cooler) right next to or on your work station. That way, you'll ahve to go farther to feed your habit. I don't know how far you'll ahve to go, but its just a matter of adding tiny bits of resistance to getting coke and make getting healthier alternatives easier.
BTW, availability increases consumption, and that's one of the reasons why you find coke or similar products EVERYWHERE. The soft drink people know this and that's why they make so much money selling sugared water. I'm not anti-soft drink, though; I strongly believe people should make their own choices about drinking more or less, but it is a little ridiculous how well these guys play this game and how well tehy're doing. If you're interested, look up the quarterly (or annual) profits for Coca Cola (Stock market: KO). You might even consider buying some shares if the price is right, seeing as you know first hand how well their product works.
