Not a chance. :)

Water puts out fire by cooling the source of the fire and by depriving it of the oxygen molecules that feed it. Stars are not on fire though. Fire is caused by chemical combustion while stars are fueled by fusion. The Sun's energy is created in its core by fusing together hydrogen nuclei, and this is enabled by the immense gravity of the Sun. Adding water would merely add additional gravity. Plus, the intense radiation of any star would break up the water molecules into hydrogen and oxygen, which are already abundant in the Sun's plasma.