When J was sick a couple weeks ago with a viral infection, he had a high fever and didn't want to eat anything. Food - especially solids - made him gag. But I had to force calories into him somehow. The only thing he'd take was smoothie. I blended orange juice, strawberries, banana, kale and greek yogurt. I'd also mix his medicine into the smoothie when the doctor put him on antibiotics.
Dealt with some minor weight loss and sleep training regression for a few days afterward, but we're back on track again.