Hi A....it sounds like your son has more will power than you do...you've got to win this one, or he may end up like my friend's stubborn toddler who somehow managed to thrive on little more than white grape juice and graham crackers for an entire year...I baby sat her for a few days once while her mother was away on business...It took a couple of days of refusing her constant demands for "juice, Juice, JUICE!"...but by the last day she was clearly defeated and had no problem finishing her meal at our local buffet, not to mention several additional servings of corn...I warned her mother that she would probably "poop a corncob" the next day, and she did...ha, ha...which was good, considering she was only having a couple of bowel movements per week at best...Remember, however, that toddlers begin to eat quite a bit less when they start burning off that baby fat; you have a 6 y/o son, so I'm sure you know the difference between what is normal and what is not...I'm glad that your son is not a diabetic, like I am...diabetics are only thirsty if their blood sugar is way too high...it's a natural response because urine carries away the extra sugar, so to speak...and salt too, by the way...that's what electolytes are basically, salt and sugar...and that's what I.V. fluids are too, varying amounts of salt and/or sugar...I mention this because if your son is drinking large amounts of fluids without electrolytes (no carbs or sodium) and is not eating enough solids to replenish them, that is very dangerous, even fatal...the common term is "water poisoning"...that's why you give Pedialyte to infants and Gatoraide to athletes instead of water; both groups are passing lots of fluids rapidly...it's upsetting to me that pediatricians often tell mothers what to do but not why...so I thought I should mention it, considering the trend towards eliminating carbs and sodium from beverages whenever possible...I hope you found this helpful...I served as a medic at the BAMC Pediatric ICU for 3 years, and I have 3 children (2 adults and 1 teenager) and 1 goofy granddaughter...So, toughen up, Gal! You've got about 3 ft. on him; you can take him!...ha, ha...lots of luck.