Caffeine will dehydrate you... Also, electrolytes can be imbalanced even though they show "normal" on a blood test. Magnesium, for example, is very hard to really measure because blood levels do not reflect tissue levels at all. Also, inflammation of mucus membranes can increase water loss and cause the sensation of needing more water. And Lyme can cause Sicca Syndrome (aka Sjogren's Syndrome), which is dryness of the mouth and eyes.
I think it would be worth it to try the Pedialyte and see what happens. Good luck,
Chronic Lyme Disease, Chronic Bartonella (clinical dx only), Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD ("Secondary Lupus-Like Syndrome"), Osteoporosis, chronic Lymphopenia, etc.; G-Tube; Currently trying to wean off TPN.
Meds: Pulmicort, IV Ceftazidime, Heparin (to flush PICC line), Claritin, Domperidone, Colloidal Silver (used topically), probiotics, Milk Thistle, homeopathy.