Most commercial stain removers are capable of breaking up sap stains. A little bit of your everyday liquid laundry detergent may also work. Transfer the stain remover with a rag or cotton ball. Spread it thinly over the area you need to clean. Work the stain remover into the stain with your fingers or a toothbrush, if you’d like. Leave the clothing to dry in open air for at least 20 minutes. This gives the product time to loosen the dried sap, which is very difficult to remove through washing alone. The temperature you use depends on the kind of fabric you’re washing. Most clothing can be washed in warm water, which is usually enough to remove sap stains. Delicates and darks should be washed in cold water. Washing can be done either in a washing machine or by hand. Your regular laundry detergent is normally enough to remove sap stains. For extra effect, you may use bleach. Chlorine bleach is safe to use on white cotton or cotton-polyester blends. You’ll need an all-color or oxygen bleach for any other type of clothing. Read the label information to ensure the product won’t damage your clothing. No matter how tempted you feel, don’t throw a stained shirt in the dryer. As soon as that stain dries, it’ll be a nightmare to remove, especially if you used heat. Wash the clothing again or try isopropyl alcohol. It may take 2 or 3 rounds to fully remove the sap, but you’ll save a perfectly good piece of clothing.

TL;DR in Chinese:
用去污剂预处理汁液污渍。 将汁液用肥皂浸泡20分钟。 用尽可能高的水温清洗衣物。 用漂白剂洗去顽固污渍。 反复清洗直至去除汁液。