For me I feel the effect of caffeine right away and I think that is why I am afraid of it as with sugar I don't feel the effect for a few days. Caffeine makes my anxiety go through the roof. At times I could drink about 6 diet pepsis a day and then one day at work I was feeling really anxious to begin with and then I drank diet pepsi and wow that was a scary feeling. One that made me never want to touch the stuff again. And I have not touched it since (it has been about a year.)

Kari