If the fish is eating, and not spitting its food back out, odds are that it is okay. If you find that it eats but still looks swollen then skip a few feedings and see what happens. They can go a few days (and really much longer) without food without any issues.
What are you feeding them and how often? How long does it take them to consume what you put in the tank?
If it is bloat, a fish that physically looks big from "bloat" is likely past saving.
But, rememdy wise, bloat mostly results from stress, so anything you can do to reduce that may be helpful. (Separate tankmates, keep lights out, etc.)
Epsom salt is a good, non stressful and easy thing you can do. You can google it for dosages; we use a tablespoon per 10 gallons, mixed with tank water to dissolve first and added over a few hours. We have had fish look funny due to what we think was basically constipation and Epsom will help resolve this as well as various other things.
Water changes are another good starting place. A daily 50% water change will do wonders for lots of things. Change a lot of water every day for a week and that is an excellent building block for getting your fish feeling good again.
If you try those things for a few days and the fish still won't eat or spits, then you may have a more serious problem. There are lots of interweb recommendations for bloat. I like Metronidazole with daily water changes. I do not care for the Clout based remedies, as they are harsh, and I have not had good results the few times I have tried them.