Prepare plum juice. Anything is fine with plum, but these days, it is recommended to serve it as 'yellow plum'. This is because the taste and smell are better than the green plum.
However, don't believe the nonsense that plum seeds are poisonous. Of course, there is poison, but all fruits, such as apples, peaches, plums, and apricots, contain poison. You don't know how much you have to eat to die from the poison. Maybe I'll die first because I'm full. So please don't believe such a strange argument.

You can mix the plums with sugar, or you can put the plums in a container first and pour the same weight of sugar over them.
However, it is better to add a little less sugar than the amount of plum. In other words, for plum 1, 0.8 to 0.9 sugar is appropriate.
It is not recommended that you wash the plum in water and pick all the tips of the plum with a toothpick. Those who like clean things won't dry them, but if you want to drink delicious plum fermented liquid, it's better not to wash plum in water.

Plums do not necessarily have to be put in a jar. There are glass bottles, there are plastic bottles.
However, it is not recommended to drink plum fermented liquid for a year. It is also not recommended to separate plum and plum fermented liquid after 100 days. It is recommended to move it to a jar after a year later. If it was in the jar from the beginning, it is fermented and aged for three years.

The reason for fermentation and aging for three years is because of 'sugar'. Not long ago, TV reported that plum fermented liquid is "sugar water," which is equivalent to plum fermented liquid within a year. After two years, the sugar in the plum fermentation solution has changed from polysaccharide to monosaccharide, which is chemically decomposed. So sugar is sugar, but it's glucoseized.