The inpatient program that I have experience with - we were basically treating lack-of-interest ARFID - you find something that the kid enjoys (for us, it was watching a DVD of Super Why, but other kids like to play with toys) and for 30 minutes, 3 times a day, they're in a room where...
if they take a bite, they get to do the fun activity for a bit, and if they don't, then everyone just sits there calmly, and if the kid gets out of their chair, you gently return them to it. It was a four-week program; the first week, a therapist is alone in the room, and parents observe through...
a one-way mirror; next week, parents are in the room while therapist does the feeding; third week, parents do the feeding with the therapist in the room; fourth week, parents feed while therapist watches from the observation room. It went really well for us, but some of the families we met...
were on their fourth or fifth stay - things would get better for a while, and then they'd get worse. Another thing we learned is that some kids with ARFID are basically on the verge of dehydration all the time - if they start vomiting you basically have 6 hours to get them to...
keep some fluids down, or you're in the hospital for IV hydration. The program also starts with conversations with a psychiatrist, and my impression is that there's a lot more types of therapy they can also use if there's an underlying cause other than "they're never hungry and food is boring."
(We were on the very border of "ARFID has a name" so we didn't get an official ARFID diagnosis, but if it had been a few years later it's pretty clear we would have.)