What are the "last-minute" items that Cheryl remembers to bring as she sets out in Chapter 3: “Hunching in a Remotely Upright Position”?

Cheryl packs all of the items into her backpack and, when she's done, she remembers that she needs to bring a good amount of water because she didn't realize at the time of planning of her trip is that she is beginning her hike at one of the driest places on the trail and that it would take her two days to reach the first water source.