What would happen if you pour water into space?

Water poured into space (outside of a spacecraft) would rapidly vaporize or boil away. In space, where there is no air, there is no air pressure. As air pressure drops, the temperature needed to boil water becomes lower. That's why water boils much faster on a mountaintop than it does at sea level. In space, because there is no air pressure, water boils away at an extremely low temperature.