I was recently out to dinner with a friend of mine who was recalling that he hadn't actually had any water to drink for about a week and a half.
THIS IS NOT COOL.
Sure he had been fueled by coffee and soda and various other "adult" beverages that contain water, but no actual, unadulterated, H2O.
For him and all of you that may not be sipping on the good stuff, this fact's for you! From the scientific literature an article entitled, Cognitive Performance and Dehydration
"Your brain is 73% water. It takes only 2% dehydration to affect your attention, memory and other cognitive skills."
So bottom's up! Just make sure you're putting something in your body that your brain can actually use.