“Naughty figs” refers to the bad or inferior figs in Jeremiah’s vision. They may have been rotten figs or fruit of the sycamore, whose juice was bitter. In the vision their poor condition served as an emblem of rejection.
The bad figs represented King Zedekiah and the people who remained in Judah under judgment. Their inferiority contrasted with the good figs and expressed their rejected condition.
The inferior fruit may have been bad because it had decayed or because it came from the sycamore. The supplied material uses this natural distinction to explain the image in Jeremiah’s vision.