Emptying your colon pre-fast?

Hello everyone! I"ve fasted before I before and I know how during a long fast your body tends to produce feces even if you're weeks into it. It's also important to prep before your fast. I was just wondering, since I've had colonoscopies before: what if you did a colonoscopy prep with dulcolax and miralax? It would clear our your colon and then you could start your fasting if you wanted to speed up the process? Thank you was just curious :)