To efficiently wash dishes by hand using less energy and water always scrap off food from the dishes before it. Then fill a separate container/bowl with hot water and dish soap, so that water just covered the dishes. If needed you can leave the dishes to pre-soak, but not too long, so that the water still remained hot/warm. Use this soapy water to clean the dishes. To rinse the dishes use a separate container/bowl filled with clean cool water. This is more efficient than rinse dishes under a running tap.
No investments, just creating heat and water saving habit.