Is this better than a backpack?
Do you really need that backpack? The @avantclimbinginovation Snack Pack multipitch storage pouch is designed to hold snacks and a phone and is about the same size as a chalk bag. The 1L cinch-top pouch allows quick one handed access to snacks and the zipper pocket has a built in phone leash.
Check them out at https://hownot2.com/snackpack