I just brewed up a root beer batch and put it in a host of different bottles. I used 2L and 500 ml soda bottles, wide-mouth 500 ml Gatorade bottles, and 500 ml water bottles. The water bottles worked ok at keeping the carb, but their thinness caused the bottom of the bottle to push outwards so the bottom was convex. You couldn't stand the bottles up. My advice - it will work...just get some 6-pack holders or something to stand them up in the fridge.
Planned: American Wit
Secondary: Abbeyish Ale