if i'm not wrong , playing with Exult should allow you to feed the anyone using a feed hotkey(F i think). Serpent Isle with Silver add-on install (even without Exult) should have this shortcut key too.

unfortunately, it might also use a plot item to feed your character.
bootstrike.com/Ultima7bg/Online/jeff.php
With Silver Seed installed for U7.5, you can feed with the hotkey "F". Just hit the hotkey, then click on the character who is hungry. Be careful, because you may eat or drink that one item you want to save (like the bottle of Ice Wine).

That's very unlikely because the game chooses higher value food first in order to fill them up quickly, and if their stomach could be filled by the ice wine they wouldn't be complaining of hunger yet. Even if it did happen the ice wine is not a necessary item.

I can and did (and still does) happen to people though, especially if the ice wine is in the Avatar's inventory and the other food is in someone else's pack. Having the party eat all of your garlic is another potential side effect.

Never had the garlic thing happen either, nor have I heard of it happening to anyone, and I always have someone else carry the food.

However, if this does occur by some twist of fate, you can always get more garlic, or pick up any bottle of wine with the same graphic. There are dozens in Moonshade.

Personally, I think the game would have been better without the mechanic of having to eat. IMO, it adds needless inventory management and doesn't really add anything to the game, as food isn't scarce enough for it to actually be an issue. I would even consider this to be the sort of mechanic that deters me from playing the game in the first place.

Ultima 5 and 6 handled it much better. In 6, you automatically consume food when you rest (and there is only one food iteme), and you don't otherwise need it. In 5, you don't have separate character inventories, so all you need to do to eliminate food issues is to but a lot of food; no need to choose who eats it and who carries it, or which food to give to whom, or to dig through your inventory for a food item.

By the way, random fact; Ultima 5 is the only Ultima (to my knowledge) where you actually need to rest for a reason other than passing time; it is the only Ultima that requires rest to recharge MP. In every other Ultima (excluding 0-2 for obvious reasons (lack of MP), and I haven't played 8 or 9), MP recovers on its own over time.

I have the same problem. What do I need to do to feed my character?

A user above has already said it: double-click the food item, the mouse cursor will change, then click on the hungry person (not the inventory paper doll). That should do it. Food is used like magical items, for example.