I like feeding Pokemon with berries on gyms. However, it is not always allowed to feed them.
I already know that you cant feed more than 10 in a certain period of time. I also know that you can't keep feeding the same Pokemon over and over again. what are the limits for feeding berries to Pokemon in gyms?
10 berries per Pokémon per half hour, fixed window (so it resets after 30 minutes after the first Pokémon was fed)
Any number of Berries to ten unique Pokémon per half hour, rolling window (so each time it's been 30 minutes since you fed a Pokémon, a new one is eligible)
As you feed a Pokémon, each successive berry after the first restores less health; this is reset after thirty minutes as well (with the fixed window).
There are no known limits per Pokémon for multiple trainers: I have seen spoofed gyms being defended prior to legendary or EX raids where clearly dozens of bot-trainers are feeding berries to the same Blissey.