Free Will is arguably the internal decision created in the mind. However, there are many external influences which can affect the internal judgement, such as social constructions: conformity, authority, etc artificial inducers: drugs (medicine and illegal), shock therapy.

So one could hypothetical argue that whilst we have Free Will, people would choose free tasty cookies over the contents of a public toilet. So the feedback from the decisions created by free will are statistically measurable and thus, could be altered for you to produce a more desired outcome, such as replacing the public toilet option for £20.