Generally if you are truly dependent on caffeine you won't ever notice it as long as you keep drinking soft drinks/ coffee but if you dont get your dose for the day you can feel pretty damn shitty depending on your average daily dose of caffeine.

I'm sleepy a lot but I just like to drink water/juice, not a very big fan on coffee and soft drinks. They have little effect on me anyways so I prefer not to drink unhealthy things.