You knew the answer before you asked ;+D. All those things I mentioned came from your posting history over the years.
Since the MC is NOT a weight loss diet and it does NOT work by the restriction of calories so calories are irrelevant. It is the interaction that "anything" one adds will have with the balanced components of the MC and how it will affect digestion and the efficiency of the cleanse. The MC works in a very simple elegant wayas is. If it aint broke don't fix it.
You can add a little variety by switching from lemons to limes or mix them in different ratios. You can have it warm (not hot) Freeze it into cubes and make slushies etc.