What is the reason for Grendel throwing apples at unferth instead of batting him to death?

Grendel throws Apples at Unferth as a symbolic gesture to mock and humiliate him. By choosing a harmless action like throwing Apples instead of physically harming him, Grendel demonstrates his superiority and perhaps sees greater satisfaction in this psychological torment. Additionally, Grendel's actions reflect his cunning nature and desire to assert dominance in a non-lethal but impactful way.