The only being with free will is a being that requires nothing to survive.

Our consciousness is influenced by our body through the acts of breathing, eating, and living (using 5 senses).

If one were to find out how to survive without any inputs, they could truly exhibit free will.

Imagine we are all beings of pure consciousness (energy) and matter is a simply energy vibrating to the point where it appears to be solid. Therefore our finger still contains the same original piece of ourselves (consciousness) and could theoretically influence the surrounding environment.

Now take a plant leaf (appendage or organ) or a seed (sexual reproductive organ) and ingest that. Is it possible that plant's consciousness is now affecting your own? While the degree of affect may not be readily perceivable, it is still there.