There aren't many easy techniques to soften hard Ladoos, but you can either warm them up or crush them and try to bind them with a bit more ghee. That said, the reheating process does change the color of the ingredients. Also, if you have used thick sugar syrup, your ladoos will turn hard, and it'd be difficult to soften them later. Hence, it's recommended to follow the right recipe while making any ladoos at home.