2. After the fire boils, pour enough cold water, soak for 20 minutes, and then simmer for 10 minutes.

3. Add rock sugar and turn off the fire. Cover the pot and simmer for half an hour. Extra, take out the soup and pour out the dregs.

4. Put it in the refrigerator, or put in ice cubes and drink it directly after refrigeration.

5. If you find the color of brown sour plum soup unattractive, you can also use watermelon juice to freeze it into ice cubes, and then put it into sour plum soup, so that the color of sour plum soup looks better.