How hot can water get?
Water can be heated to 212 degrees Fahrenheit at which point it boils and changes into steam.
Water boils at 212 degrees Fahrenheit at sea level. The boiling point rises as altitude increases. Once it reaches boiling temperature, that's as hot as it gets under normal conditions. Superheating is possible, but that's a whole different scenario.
At typical air pressure near sea level, water will boil at 100 Celsius or 212 Fahrenheit. If you add a lot of salt or sugar to the water it may boil a few to many degrees higher.
The hottest temperature water can get is 100 degrees Celsius. If you continue heating water beyond that it will simply turn to steam.