I drink Pepsi, and have tried to quit many times. One major thing I notice when I'm "on it" is that I get super drowsy a couple hours after lunch every day. When I'm off Pepsi/caffeine, I don't get this afternoon drowsiness. However, It's really hard to stay up after 10pm when I am off Pepsi/caffeine, which is when I work on my personal projects..
What you're describing is sugar dependence, not caffiene. Cut out all processed sugar and after 2 weeks you'll wonder what drug you are on (then cut out "healthy" carbs like bread and pasta and you'll wonder how you ever wanted to eat them).
I get those symptoms from coffee. I don't eat processed sugar and I mostly avoid other carbs during the work week. When I don't drink coffee I don't need an afternoon nap. But I like both coffee and naps so I often have coffee.
