The best Korean acid toner is COSRX AHA/BHA Clarifying Treatment Toner. Formulated with 10% of Apple Fruit Water (AHA) & 10% of Willow Bark Water (BHA), the formula gently exfoliates dull skin, removes dead skin cells, gets rid of acne scars, and prevents the early development of whiteheads and blackheads. This toner is also alcohol-free, so it’s great for sensitive skin types!