I had never seen nor heard of this item before this morning, but it is a very simple solution to the endless question of “how best to shower using very little water”.
This item fits a 1 or 2 liter bottle of water, also the Platypus collapsibles, and currently only about $14, including s&h.
My favorite way of minimalist showering when traveling is to use a large, premoistened washcloth...like those marketed for bedridden individuals...squirted with just a little of my favorite body wash.
Wash, discard the washcloth, rinse.
I would bet that 1 liter of water would provide an adequate and refreshing rinse, and you could set it outside in the sun to warm.
If very remote and feeling especially daring, strip down under a hospitable tree and have at it.
Or, in your own shower, with or without standing in a small basin to catch rinse water that can then be disposed of under a nearby welcoming bush or tree.