I drank too much water and just after that had warm chocolate milk..
the milk was not tasty or ..! sweet..?!
Is there any scientific reason or just that my mumma added less sugar or maybe forgot to add some.!

Dear student,
When we drink water it goes into the stomach, we taste chocolate milk through taste bud which is in our mouth. So after drinking water the taste of chocolate milk will not change, may be less sugar or no sugar is added in milk due to which it is less sweet.

Regards