It's best to put rock sugar in the boiled mung bean soup. Rock sugar reduces the fire, and its calorie is lower than that of white sugar, so it won't be easy to get fat after eating. When putting rock sugar, wait until the mung bean soup is cooked and turn off the fire before putting it in. Use the temperature in the soup to melt the rock sugar. Besides controlling the time of putting sugar, we can also make mung beans easier to boil through some tips.