1. Materials needed for preparation: one bottle of rice vinegar, three green apples, and appropriate amount of rock sugar.

2. Wash the apples, dry them and slice them.

3. Then cut the apple slices into dices (directly cut into thin skins).

4. Put a small portion of diced apples into the bottle first.

5. Add another layer of rock sugar.

6. Put a layer of apples and a layer of rock sugar in the bottle in the same way.

7. Pour the rice vinegar into the bottle.

8. The amount of vinegar is not enough, so the ingredients are better.

9. Cover the bottle with plastic wrap and just cover it.