Drugs. Clearly any thing that would cause furtehr damage to theliver-alcohol being the prime thing. Nausea and vomiting are side effects so should limit any food that cuses this in you.
Food. I assume you are taking interferon for hepatitis c infection. There is really nothing special to avoid while using interferon. But make sure you are well hydrated, drink plenty of fluids. Try to avoid any spicy food, since it can cause upset stomach (interferon can also cause upset stomach). Avoid alcohol completely.