Yep, just ask for a cup of ice water at any CS restaurant. (I've found that, depending on how the restaurant counter is set up, you don't even have to wait in line if you're only getting water. I've walked up to the place where you pick up your food, and asked for a cup of water from the people working the beverage area. They seem happy to give you water even if you don't order other food.)
But this works best if you have a "wide mouth" water bottle. It's much harder to pour water from a cup into a narrow-mouth bottle.