I have used solar showers many times when kayaking and touring by bike if I am offered the use of someone else’s, but they will only work is they are left in the sun during the heat of the day and that mean hauling the water while riding. I don’t carry one on tour. I have a 1.5 liter wide mouth Nalgene bottle I carry in one of those oversize water bottle cages and a soft wide mouth 1.5 liter Nalgene canteen. I fill both to the top and then pour about 600 to 700 ml from one into a pot and bring it to a boil with my home made alcohol stove. I pour the boiling water back into the bottle and throw a jersey or something over it to keep the water warm. I repeat the process with the second bottle. I fashioned a shower spout with parts from REI and the local ACE hardware store and an extra Nalgene top. I get wet with the soft bottle and soap up (with my bike shorts on if I am in a crowded camp ground). Then I pour the hot water from the hard bottle into the soft bottle and rise. Three liters seems to be plenty of water.

The water doesn’t have to be potable, but it does have to be available. No water, no Shower!