Hi Phoebii mummy,
When my son rejects his medication, I will mix it into his milk. I will make lesser milk so that we will finish the whole amount. Eg, if he always drink 120ml at one go, I will make it to 60ml then add the medication. (Coz when he is sick, he always cannot finish 120ml at one go)
The other way is to mix it into his cereal or porridge. I will apportion one small portion of porridge out then mix in the medicine and finish feeding that portion first.
Hope your dear son gets well soon. Take care of yourself too.