Learn German: Mit reifen Trauben kann man Wein machen. - You can make wine with ripe grapes.

The preposition mit always triggers the dative case. We are using the plural noun Trauben (grapes) without an article (this is called the zero article). In the dative case, adjectives before a plural noun with no article take the ending -en.

Do we need to add a dative plural -n to Trauben?

You are right to think of that! In the dative plural, German nouns usually get an extra -n added to the end. However, because the normal plural form of Traube is already Trauben, it already ends in -n, so we do not add another one.

Why is the verb kann before the subject man?

In a German main clause, the conjugated verb must always be in the second position. Here, the entire phrase Mit reifen Trauben (With ripe grapes) takes up the first position. So, the verb kann must come next, pushing the subject man (you/one) into the third position.

Why does Wein have no article here?

Just like in English, we leave the article out when talking about an uncountable noun in a general sense. We are talking about making wine in general, not a specific wine, so we use no article.