Great thread idea! Going to contribute some (prices are current/approximate so may change over time). FYI not using referring links just shortened links.
GREAT: portable battery-powered showerhead ($31+) -
http://a.co/bx6aqrD
Our go-to camping spot about 20min from our house is a campgrounds that has showers, but recently we went on a 4-day overlanding trip with new friends [that we met here on OB!] and decided to bring a way to rinse off at least. We actually got the Ivation brand version for $40 but it looks like one of those imported products that are all identical and just have different brand names/labels on them, so I'd just get one of the $30 ones and they'll likely be identical. So we brought this and a black 5 gallon bucket (few bucks at Home Depot) filled with water. We left the bucket in the sun to bake and then opened up, turned on the motor of the showerhead then dropped it in. It doesn't spray water pressure like a real shower at home obviously, but it was very impressive still, definitely way better than one of those black bags you hang from a tree that relies on gravity alone. Our new friends agreed (even though at first I think they thought it was "overpacking" haha). After using it to rinse off your head/hair and wash your face proper with warm water, everyone agreed it was worth its weight in gold at a campsite. We will always have one of these with us camping/overlanding from now on! It doesn't have a filter so it wouldn't be great to dunk in a creek for use (i.e. while backpacking), but we read online that some people just wrap a coffee filter around it with a rubberband, which sounds reasonable. The unit has an internal rechargeable battery that you can charge via USB (like from your vehicle's USB/cigarette adapter or from a solar USB connection), and it comes with a suction cup and hook to attach to vehicles or trees. Oh also, it doesn't heat the water, only sprays it. The black bucket didn't get the water too warm (5 gallons is a lot to heat up even sitting in the sun), but if we wanted warmer water we could have just boiled a pot and dumped it in to mix etc. Best setup might be a metal black bucket of some sort? That way you could literally hang/mount over a small flame to warm it up? ...or toss some hot coals in to warm up...?