In the Wild Area near the Day Care Center are two characters called the Digging Duo. For a price of 500 W, they give one or more items, the quantity and type of which is (or seems) random, varying depending on which of the two is chosen. These items can be found, for example, here on serebii.net.
Having spent now over 50,000 W, I have gotten most of the items in large quantities, except for Gold Bottle Caps, which leads me to believe that every type of item has its own odds of getting rewarded.
Has datamining revealed what the odds for the Digging Duo are, both for items and quantity mined?
Best Answer
As far as Serebii datamined, they found only the focused one had any chance of fetching the gold bottle caps. On the image shown beyond, we can see a 0% to get the golden cap. This is most likely false since some people got it, yet it must be less than 1% hence it's very rare status.
This reddit link got some more data. But the most you can learn from it (except the datasheet link there) is that there is a special animation when you dig it.