It seems to work no matter where you are and what you are doing. Ensure that the character to eat the food is the one highlighted white on the Inventory page - like equipping, BG3 uses the 'magic hand' to have characters interact with equipment carried by someone else. I wasted a few healing potions by clicking 'drink' and then realising that a perfectly healthy character was highlighted and was gulping the potion, presumably whilst laughing at the character bleeding to death.
