Chances are your vomiting episode was caused by a build up of toxins rather than the drink itself. Yet, I know that once that happens the drink will lose its appeal quickly. When a lot of toxic material is dumped into the digestive system all at once a reflux reaction can push that waste into the stomach and either cause sudden and violent vomiting, or a lingering nausea where you think you would feel better if you could throw up. This reaction is quite common in many cleanses, not just fasting. Many liver flushers go through the same thing and blame the drink.
My recommendation would be to either switch to a juice fast or a raw diet for a week or two and allow your body to detox more gently. After that, start using the Master-Cleanse drink for one meal replacement, then two, then use it for snacks while still having either a glass of fresh pressed veggie juice or a raw salad once a day. If this works, then you can try going back to the MC. The longer you eat healthy and gently cleanse, the easier subsequent fasts will be. Cleansing is a long process, not a quick fix. Staying clean is a lifetime commitment.