What is the right time to have coconut water, having it after meal or in afternoon or night leads to acidity and cold?

No perfect time: But consider using coconut water only when you need extra electrolytes, like after working out. To be honest, there is no clear benefit to coconut water over just plain water. In fact, the extra calories of coconut water could create more problems than water alone, for those trying to lose weight.

Whenever: coconut water is just sugar water. You can have it when you want it. It has less sugar than many other drinks, but there is a case for Americans having too much sugar in their diet. Sugar causes a surge in insulin which grows fat cells. That said coconut water has less sugar than many other beverages.