The 2L soda bottles, while exceedingly durable, don't have a great form factor for packing. I'd go with a couple of bladders, as it will be easier to get into a pack.
This bag, or one of the other two similar to it, held 63L of water when we left the ground. It was mostly 2L soda bottles, though I can't say where that extra 1L came from, but that's the number in my notes.
[And, let me tell you, walking out of a grocery store with a shopping cart full of soda, and then opening up all those bottles and pouring the contents on the ground will certainly garner some attention.]
These loads were not fun to ferry up to the cliff face, and were brutal to haul up the face, especially in the couple of sections that were less than vertical. When we got back on the ground, I think we only had something like 2L remaining.
Days without access to water? Yeah, not fun. I don't envy you, OP.