You can use a portable shower that uses solar energy to heat the water. Solar showers are convenient for camping and backpacking. You can hang one out by your swimming pool for a quick, simple rinse. To use a solar shower, follow these steps:
Fill a specially constructed plastic bag with water and then place it in direct sunlight to heat up.
The top of the 5-gallon bag is clear, and the back wall is black to absorb maximum sunlight. To warm the water of your portable shower, simply position the bag so that the clear top faces the sun. Most portable showers come with a thermometer so you know when the water’s reached a comfortable temperature.
When the water’s hot enough, hang the bag from a tree for a gravity-fed, hot shower.
Portable showers can get really hot, over 120°F, so beware. Always sample the temperature before you step in.