I've already had an ACTH test, diabetes insipidus, A1C, and the other usual suspects. All tests are normal. These symptoms started around 20 years ago. It has had ups and downs. When I finally did manage to make it to the cardiologist (for POTS) they told me to 'push myself' and 'exercise'. Can't drink plain water because it makes me nauseous. If I substitute gatorade for another sports drink, with a lot of potassium, I become extremely nauseous.
While walking (from the parking garage) to the University of Maryland Medical I got lost, because I'm 'out of it'. But if you let me lie down I will 'come back', also brain comes back online and thirst signals are more prominent. If I could lie down all day, I would be normal. This is how I got through high school btw....
Only use the powder gatorade, and only use 60% of the recommended amount (I drink out of a 64oz gatorade container, more convenient). When I was at the holistic DR in 2013 they also mentioned some of the things other posters have mentioned, like drinking for blood sugar reasons, etc. Was on flourinef 20 years ago, don't remember the result. Ritalin does briefly help symptoms, but can crash afterwards because it retards thirst.