You joke, but old school nurses do just that: mix prune juice, coffee, and milk of magnesia. They call this combo “The Bomb” lol: https://drslusher.com/constipation-remedy-or-the-bomb/

I’m more inclined to tell you that while I appreciate your commitment to a natural remedy, Miralax (polyethylene glycol powder) is the most effective remedy in my personal experience as a nurse. For what it’s worth.