The sports bottles really helped me in the early days. It might just be a guy thing but I found I had the nipple in my mouth constantly until it was empty LOL
Seriously though hydration is a huge part of post op life. If you are not hydrated your weight loss will not be maximised, and your general health will be eventually be affected, maybe even irrevocably and might even lead to kidney output reduction or failure.
So I know its a pain in the backside but you must find a flavoured water that you can get down, and then get at least 2l down your neck each day by sipping throughout the day