Actually the fungal infection is near her beak and has started drying.What is the fungal infection? Where is the fungus? Which medication is he taking? Fungicides (antibiotics don't do anything for fungal infections) generally aren't bad about making a bird nauseous, but there can be exceptions. Some antibiotics can make a bird pretty nauseous.
Try giving him some food before medicating and if that doesn't work call your vet and he may want to change the fungicide.
Be sure you don't feed anything with sugar in it while medicating for fungus - fungus thrived on sugar.
Ok, I will stop giving her apple and will update you about her health.. ThanksApples are very high in sugar and carbohydrates (carbohydrates metabolize directly into sugar) - so no apples. All fruits have a lot of sugar, so just skip them until he is well. Beets have 6/10th the amount of sugar as apples - not good - and enough carbohydrates that they are not ideal.
Why don't you just cut out all fruits until his fungal infection is cured?