I was going to suggest banana but I guess not. I’ve had some luck with putting a little honey at the end of the syringe & going from there but Idk if that will work. I would call the vet & ask.

Refusal of banana?! Geez Rookie means business! If Rookie is old enough to eat veggies, try the bunny burrito but take a very flavorful/smelly veggie like cilantro or basil (if he likes either of those) and really rub in the scent all over the end of the syringe. You can even wrap the veggie around the end of the syringe a bit. Hopefully he will smell the veggie and be interested enough to not bury his head long enough for you to give him his dose.

This probably sounds crazy, but have you tried to offer him the syringe without restraining him? Luna will only take medicine if I don’t touch her. If I walk in the room she will hop over and I will sit and hold the syringe at her eye level and she will start gnawing at the syringe to get at the medicine. It’s still tricky though because she only takes it straight on like a bottle, not on the side of the mouth. So to avoid aspirating the meds I basically just push a couple drops out at a time – I have to push the plunger extra slow and take care not to accidentally push it too much when she tries to grab the syringe out of my hand. I admit the method is not for everyone, but Luna and I have done it so many times that we are comfortable and feel safe doing it this way, and it is the only way we have known.

Another possible idea, Amelia loves the apple banana flavored critical care, like slurps it out of the bowl loves. Perhaps mixing his meds in a small amount of critical care and letting him eat it like a porridge