If your body can tell the difference between "I pour poison down your throat while you are unconscious" and "I pour nutritious broth down your throat while unconscious" (one results in a fort save, one doesn't) then I have no problem with your pre-rational mind being able to differentiate between harmful and non-harmful effects and make a will save for the former and not the latter.
So I'm just going to ask the player if they want to make a save, or make a choice for an NPC, if this comes up. I have no problem with unconscious people making fort or will saves, but reflex is pushing it (though in a particularly farcical game, I would allow "Weekend at Bernies" style shenanigans, I guess.)
No matter what the rule is, I'm going to play it this way anyway.
That's why I specified saves, however. The broth, in the gaming sense, doesn't require a save. Much like you can't resist a geas/quest if someone has you unconcious for ten minutes, you can't resist broth either. No save means nothing to resist.
But do note you could resist a potion of cure light wounds. You just choose not to, as a player. That's what I'm referring to. Your body doesn't actually know it's not harmful, you must conciously choose to fail a Will save to get the full effect of cure light wounds, for example.
The game already assumes you save against everything that allows a save. It just allows you to willingly fail a saving throw at any moment, for those spells/effects that are beneficial. I'd remove that choice for unconcious characters, much like how it is removed for a raging barbarian with the Superstition rage power.