Let's see. As a child, some family lived on a farm. No running water. No indoor plumbing. Coal stove. So you heated water for bathing on the stove. At night, and especially in the winter, you used a chamber pot. But hey, they had electricity!

And a couple decades ago, living off the grid in the US, it was sometimes pretty much the same. One winter, I lived in a tipi. There was a communal outhouse. But hey, I did have a down bag.

So whatever, any well-equipped van would have a composting toilet. And a solar-heated water tank, with a portable shower. Just like RV stuff, but on a smaller scale.