Many water bottles are softish, thin plastic. But some are thick and solid, like soda bottles, thick PET, such as the original Aquafina bottles. Much too good for single use/recycling. Some of those iced tea bottles are even heftier, crazy durable, and have a wider mouth.
I'd use those over the thin water bottles, although either should work fine. Once frozen you can store them horizontally, stacked, or inside a box for easier handling/storing.
I like using the 48 oz squat cottage cheese containers as they stack 3-4 high, or the 4 or 5 quart ice cream tubs. And you only need to defrost them just enough for the block of ice to release itself from the sides and bottom (by placing one in a pot with some hot water for a couple minutes). Then dump the chunk and all into your starter wort pot.