Whenever i drink coke or coffee i feel tired after and I usually am trying to stay awake, so it sucks for it to have the opposite effect... Also sometimes it's like 4 pm and i'll have coke/coffee and i'll feel tired after =S
As our bodies comes down from the cup of caffeine fix, it makes us tired. It is like a drug. You feel good while you are taking it and awful when it wears off.
Also, as most of us know, caffeine is also a diuretic. So if you are somewhat So if you are somewhat dehydrated the caffeine will not have enough blood volume to shrink down the vessels to increase your blood pressure. The caffeine will then increase your dehydration andin fact make you sleepy as hell.
that happens to me too. i actually tend to drink more coffee at night, im in bed. and like victorian tea party said, its like a drug. or even a energy shot. you feel hyped up for a bit. one reason a lot of mothers or woman drink it is to get going on the housework, and to feel ready for when the kids get up for school. afterwards, your crashing, you get a sleepy feeling and just want to go to bed.
Caffiene takes energy away fromt he energy pool you have every day which means that later that day you will crash. And the energy you get at that moment may not feel like your wide awake, maybe the opposite, but it wont give you a complete sleep if you do sleep while energized.
Drinking caffeine doesn't seem to always make us feel energized or awake, if you think of it as a drug , it could of been a come down for the drug which made you feel drousy or tired.