I did a 108-mile ride a couple of weekends ago from Mass into NH and back, and realized this would be a problem as soon as I needed to pee! Dipped into some forested area for that need. It was a cool day, so my two large water bottles pretty much held up (I ran out with about 15 miles to do, but that was okay). Convenience stores are mostly open around here, so I could have procured more if I needed to. I'm planning a 200k ride soon, and it'll certainly be warmer, so I'll need to ensure that water purchasing will be possible.