Homemade DIY Rapeseed Sour: Eat Rapeseed Sour in summer, it is sweet and sour, green and crisp, cool and reduces inflammation. Preparation method: Wash and slice the tender white radish, add salt to remove the bitterness, boil some boiling water and wait until it cools down. Generally, two pounds of rock sugar and half a bottle of white vinegar are needed for two radishes. Then put it in the can for about three or four days and it will be ready to eat, sweet and sour.