Fasting can actually help recovery. But no matter if you eat what you can or nothing at all it is absolutely necessary to get enough water, salt, and potassium.
Something that might go down easy is plain canned beans, just make sure to drain and rinse them and maybe even soak them a little to minimize intestinal issues. Plain quinoa or lentils made in a rice cooker or pot with just water and salt could also be good.
Sometimes your hear about the BRAT diet. I’d recommend against it, it is very nutritionally poor so it will not give you much energy if you can only handle eating a little.