The beverages allowed while doing the HCG diet are coffee, tea and water only. Here are some advice about what water to have:

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Mineral Water
In Pounds and Inches, Dr. Simeons says that you must drink mineral water during Phase 2 of the diet. However as Dr. Simeons initial tests took place decades ago,  “mineral water” then is not the same as it is now. Mineral water today is usually carbonated and may contain other additives restricted in phase 1 of the HCG Diet.

Spring Water
The “mineral water” Dr. Simeons was referring to is “spring water” today. It’s labeled as such in stores, and is not to be confused with distilled water or jugs labeled “drinking water.”

Tap Water
Try and purify your tap water as much as possible. Obviously what’s important is that you only drink clean, pure water.