The description of Holy Water (p. 151 of the PHB) states:
As an action, you can splash the contents of this flask onto a creature within 5 feet of you or throw it up to 20 feet, shattering it on impact. In either case, make a ranged attack against a target creature, treating the holy water as an improvised weapon. If the target is a fiend or undead, it takes 2d6 radiant damage.
So, 2d6 damage at range for 25gp, not the worst thing out there, that you can throw and shatter or for some reason splash…
The throw explicitly shatters, but the word they use is 'splash'. Not 'empty', not 'pour out', but 'splash'. Is there anything, explicitly, RAW, making the splash leave you with nothing but a 2cp empty flask, rather than a still almost full flask of holy water?
Best Answer
The contents means "what's in the flask"
The contents, not modified by "some of" or "a fraction of" implies all of it. (That is a plain English reading of that clause).
Another example of this usage would be when my beer spilled on Monday night. You can honestly say that
That means that all of the beer was on the counter (and soon thereafter, some of it was dripping onto the floor).