“Pack as if you're going out for only a week during the summer. Then add what you'd need if you were going out for only a week in winter. That should pretty much cover everything.” –MrNoodly1)
“I can't be prepared for everything I can possibly imagine, so I prepare for things that are most likely to happen.” – MrNoodly2)
Minimum: Anything that can make and take calls and texts.
Upgrade: A smartphone, even one without a SIM card or data plan, can be very useful for vandwellers. Built in GPS and the ability to use offline navigation. Google Voice can provide text and calling if you get near wifi.
Related: intermittent bandwidth, bandwidth frugality,
Consider this saying: if you have water you have many problems. If you don't have water you have one problem.
Minimum: some water to drink. Can be bottled, bulk from a dispenser, etc.
* sleeping * eating * cooking * pooping