Tesco’s sell 2litre fizzy water at 17p a bottle, so if you are happy to drink 2L at a time then they’re cheap bottles!
I bought 10 of the 2L still water bottles (also 17p) to use for a batch of elderflower champagne - first time and not tasted it yet, but my point is that the bottles are taking a great deal of pressure.
As an aside - I didn’t waste the still Tesco’s water but used it for my Razorback IPA brew as it’s harder than my tap water. That is still fermenting very slowly after 28 days (now at 1.008 against a target 1.005).