The liquid floating around in the helmet would have eventually drowned him. Doing nothing was 100% certain death; the liquid water was effectively toxic.
Drinking the liquid (which may have been toxic) would have prevented the drowning and provided more time to evacuate him to the interior of ISS. If the liquid were poisonous, medical attention could then be rendered and an evacuation to Earth would be possible.
This is similar to being stranded in the wild: it is always better to drink even smelly water than to die of dehydration. You will most likely be found and returned to civilization before any toxic effect or biological infection from the water you drink would cause any serious health risks. Not drinking could cause your death in a few hours, toxic water would usually take at least a few days to a week to kill you (if you remain untreated).
This of course ignoring the entire question of HOW to drink the water.
If I were NASA I'd take a two-step approach to the issue:
1. Fix the damed leaks.
2. Install a large hydroscopic surface area water/air separator inside the helmet with a straw within reach of the astronaut's mouth. In emergency you can breath through the straw.
Regardless of this issue, it is apparent that the astronauts need an external "man down" signaling device they can activate from muscle memory. The device needs to alert on each of: the comms frequency, visually (flashing light) and on some other dedicated emergency radio frequency with detectors both within the station as well as on Earth.