There are no serious negative side effects as long its not too hot, and only issue from drinking too much hot water or any water is spending more of your time rushing to washroom.
Else in moderate quantity it has lot of health benefits such as - improve sinus health,helps fight cold, reduce pain and healthy skin by improving blood circulation, healthy digestive system,detoxification,help body fight infections, helps body cell in absorbing nutrients, and also helps in weight loss...and in case you are addicted to tea or coffee ,it can serve as good replacement.
So you just have to make sure that your water is at the right temperature and there you have a one of the best health drinks one could ever get, and its cheaper
to other health drinks by alot.