Answer:
Let me attempt to answer your question
Drinking too much water would mean that more water would be absorbed and end up in the intracellular compartment. The chief ion extracellularly is Sodium,which is "water-loving"
The doctors give a sodium IV solution (hypertonic) so that there would be more sodium extracellularly to extract water from the intracellular compartment from where water can be more easily excreted.