The benefits of drinking warm water are clearly mentioned in Ayurveda.
Warm water stimulates appetite, helps indigestion, flatulence, cleans the urinary bladder, good for some diseases like throat infection, cough, fever, hiccups, running nose, accumulation of undigested materials etc.
It can also be fortified with some easily available spices in your kitchen so that you can keep infections at bay.
Find articles & recipes for making immunity boosting water in this section.