What are the safest home remedies for cholera?

There may not be: Cholera is a bacteria called vibrio cholera.It likes alkaline pH i.e. Acid stops its growth (like cola and limeade). But you need a stomach and intestine that handle them. Unfortunately, these patients vomit a lot. The main treatment is antibiotics. Washing vegetables in acidic solutions like permenganate is used in areas of epidemics. Hand washing is a must to stop transfer of bacteria to mouth.

Rehydration: Most healthy people don't get into trouble from cholera - in fact most healthy people, due to their healthy stomach acidity, don't even get cholera. If you are unlucky enough to get it, the principle symptom is profuse, water, diarrhea, so rehydration is key. Using a "rehydration solution" (combination of (safe) water, sugar, salt, and pinch of baking soda) can be life saving!