As we know by this point, Jeremiah's God, like Guns n' Roses, has an immense "Appetite for Destruction." So naturally, he compares humans to easily smash-able wine jars and earthenware jugs. This also shows that humans are like vessels, in that they're meant to hold certain things: devotion or the knowledge of God, ideally. But instead, God punishes them for their sins by filling them with drunkenness and confusion and smashing them against each other (13:12-14).
In Chapter 18, God also compares himself to a potter. Clay is the ultimate shape-able stuff. If the pot God's making gets deformed, he'll simply smash it and then soften the clay and remake it into a new pot. It's a perfect metaphor for what he's doing to Judah: smashing it with the Babylonian invasion, softening it and then shaping it with life in exile, before finally remaking it and allowing the Judeans to return home renewed and full of longing for God.