So, everyone knows how gross the water fountain water is inside WDW and knows to take bottled water when possible but what happens when you drink it all? Well, I recommend drink mixes. Just fill up your now empty water bottle and add the drink mix. This will help with the disgusting flavor and the luke warm temperature. Everyone sells these, name brand and store brand.
For our 21 days remaining gift, I bought everyone their own drink mixes. I bought Weylert's Diet Peach tea for $1 at Dollar General, Walmart brand sugar-free Cherry drink and tea with lemon for $1.74 each, and 3 different flavors of sugar-free Hawaiian punch for $1 each at Dollar Tree. In all, I bought 6 boxes of drink mixes at a total of $7.48.
I have heard that any of the counter service restaurants will give you free ice water but I have not tested this myself.