How is water transferred from outside the suit to inside the suit?
Apollo suits had a "food/drink port" but it was apparently never used. The main purpose of the port was to allow the crew to eat and drink in a contingency situation where the vehicle was depressurized and they had to survive in the suits for an extended period of time.
In case of complete loss of cabin pressure during a mission, the crewmen might be required to wear pressurized suits continuously for as long as 115 hours. Water would be available by passing the probe of the potable-water dispenser through the helmet feedport.
Current US suits have an internal drink bag.