That's way less ridiculous than the original guys phrasing made the situation seem.
A fountain has no inherent need for non-carbonated water unless they serve uncarbonated drinks like orange or punch.
Still, in either country we run mostly safe, drinkable water through our toilets and not soda =D
Pro tip: you get the DD promo by signing a pledge sheet at Guest services at any concourse, but the coupons are only accepted at a few designated stands (on Club level, only the stand by section 230).
There are also some water fountains -- in Club, above section 202, by the bathrooms at 210 and 220, and the group area around 231, IIRC).
Good point on the coupon/wristband distinction.
Coffee and hot chocolate (and tea?) are other options printed right on the coupon.
Not-so-fun fact: you cannot redeem the wristband for water. You literally have to get soda.