Yes - any non caffeinated, sugar free beverages. I personaly prefer Mio and propel. And with all due respect to your doc, you may want to shoot for 64 oz - thats usually the recommended minimum especially for WLS patients since we dont get a whole lot of fluids from food anymore.
Also if you go to Walmart they have their version of Mio which is a little less expensive. I wanted to post this mainly to ask whether or not you are prone to headaches. I used to have them a lot and found out that it was the aspartame in products such as Crystal Light that was causing them. Walmart has drink mixes made with splenda or stevia and are both very good. Also I might suggest that at Walmart or Target you can also find Arnold Palmer's half and half which is half ice tea and have lemonade. Very tasty. You put lemons in ice tea so this just takes it one step farther and uses lemonade instead of just lemon. They have it usually for a little more than $2 for a 10 pack and usually you find it in the coffee aisle with the teas. It is actually an Arizona Ice Tea brand with Arnold Palmer's name on it and is made with Splenda.
Isn’t it a bit unnerving that doctors call what they do their “practice”? - George Carlin
I'm glad you brought up the aspartame issue...personally, many years ago I found that when I drank alot of Crystal Light, it made me depressed. It can effect different people differently, so just something to be aware of :)