I admit that I cannot choke down 64+oz plain ol' water in a day...
But club soda, sparkling water, seltzer - that's another thing. 100 oz is easy!
I have found that adding just a splash of sparkling flavored (0 calorie) water to the already bubbly water makes it go down even easier & with flavor to boot! Being ever frugal, and at my grocer's suggestion, I have begun to make seltzer at home. It's wonderful and doesn't have the sodium of commercial club soda. SF flavors also available (as are sugared for everyone else). Check out sodaclub dot com.
Sloshing while shaking-