I've stopped drinking coffee at all and I'm way less tired. Before doing this, I wasn't able to start to watch a film in the evening without falling asleep.
I tried that for a month. I was exhausted, until I started drinking coffee again. I'm not usually a heavy drinker either: a couple of cups, usually before noon.
My experience is similar. If I have coffee or tea after lunch, I have trouble falling asleep at night. However soda or iced tea seems to have no effect sleepwise.