For example, if you're allocating patients in control and treatment group based on a roll of dice - the dice don't have free will, but they are influencing the "system" of the patients and their treatment, while that system is not causually influencing the dice rolls.
For another example, if a baby is "experimenting" by babbling (a key part of language acquisition, https://en.wikipedia.org/wiki/Babbling), it's not necessary or relevant to decide whether free will is involved, the baby obtains useful experimental results of what sound experiences are caused by which attempts to move the tongue/mouth/etc, even if there's no free will and the attempts to move the tongue/mouth/etc are also deterministically caused by the sensory experiences of the baby.
That's actually the point!
Whether you swing the bat or just watch it hit the ball into the sky, you have the prerequisites needed to reason about the interaction.
A more entertaining question is how a system comes to believe causality (i.e. comes to believe that things can and must have causes)