Well, I'm not an expert, but I also noticed this problem. Look at its ingredients, including dried tangerine peel, licorice, salt and so on. These ingredients themselves have some antiseptic effects, and they are said to be the imperial formula of the Qing Dynasty. It's so expensive to sell a small bottle, and the material is good, like Master Kong's, which is much cheaper. Its ingredients are not so particular, there are several kinds.

The most important thing is to cook sour plum soup. If it's homemade, stew it for 5 or 6 minutes. I think it's better to combine high-temperature sterilization process with better technology and raw materials.

In fact, as long as you are willing to pay a little cost, this kind of thing is not difficult! The key is whether you are willing to invest. Look at those high-end pure juices, especially foreign brands, such as Guo Chun Basket. The shelf life of 100% juice is also 1 year.

Personal opinion, for reference only.