system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is that for some people drinking coffee makes them wide awake for quite some time but for others it makes them tired?

I finished my coffee about 15 minutes ago and I feel more exhausted now than before I drank it. This happens every time I drink coffee.
gpt
The caffeine in coffee stimulates neurotransmitters that have to do with alrtness.  It is  possible to overstimulate and drain these neurotransmitters. So if you are drinking lots of coffee and energy drinks,  that can happen.

Also for some people who have very "hyper" or "scattered" or "trouble focusing" brains (aka ADD) the stimulus from caffeine can actually help the "focus" of the brain, and it is very relaxing and even restful.