This question is both simple and not simple.

Go to the supermarket and see which store sells ternary milk or yogurt. The shorter the shelf life, the better.

Wait for the supplier who delivers the milk of this brand (there are many suppliers in supermarkets, supplying different types).

You can ask the supermarket salesperson how to contact the delivery person (I probably won’t tell you).

You can ask the supermarket salesperson when the next batch of goods will be delivered (they may give you an estimate).

Or, often stare at the supermarket.

When the milkman arrives, you don’t need to teach him the next step.

In addition, you can wander around primary schools and kindergartens, there may be spots there.

Especially when school is over, maybe set up a table to take orders.

In the same way, use whichever brand you find~~~~~~ I wish you success! ! ! !