I vomited on my last Master-Cleanse - actually, PROJECTILE vomited for the first time in my life. AT WORK, even! Thankfully I made it to the bathroom and no one else was in there. I think it is just another detox symptom.
You really should force down the drink as prescribed (that is with the Maple Syrup and cayenne pepper) at least the minimum, or your suffering might get even worse.