system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why does drinking water immediately quench the thirst, even though it hasn't reached the necessary body parts yet?
gpt
Thirst, just like other sensations like it, are just signals. You are not necessarily dehydrated, or in the case of coffee to pepp you up when tiered, is the body and brain telling your  consciousness that you need to refill something - soon.
So when the receptors in your month feel H2O, it signals the brain that "hey, what you ordered is on its way - be kind to the body now please!"

Or drinking coffe/sugary drinks gets you less fatigued even thou sugar and coffee needs to metabolize in your liver which usually takes half to a full hour before real effect.