Been here well over a decade, over the past few years, specifically the past two years.
I've at times, felt exhausted in the afternoon on occasion, generally when sitting watching the news, i'd lay down and watch on laptop, within ten minutes asleep, 2 hrs later at most wake feeling 'faintish', 'thirsty' etc.
Obviously i drink copious amounts of water (mixed in with other things - tea, coffee, etc).
If i consume straight water I don't come across tired or dehydrated.
I've never looked in to the science of such, in my mind coffee, tea includes water thus should be the same as drinking water, ergo no dehydration issues.
Anyone else gone through similar? or is it a symptom off perhaps too much caffeine (or an ingredient in such).