Large number of people have the habit to drink water in the morning, right after they wake up. Probably your parents have told you that it is very healthy.
If you have this strange habit, probably you have noticed that the water have strange taste.
The food contains sugars and proteins which cans be easily targeted by microbes and to come to pollution. Although regular water does not contain any of these nutrients and there is no explanation from which comes the strange taste in the water that stood on the nightstand over the night by your bed.