Firm wrap in swaddle or towel , syringe ready loaded , child under arm in rugby hold, syringe into mouth aimed at inside of cheek, gentle squeeze of foul medicine into cross baby. Lots of cuddles with reproachful eyes looking at you. There are some videos on YouTube.
I have no helpful advice, just to say I share your pain, dd (2.10) has infected chicken pox and is on the same meds. I am using the towel and syringe approach and a sweet as a reward with very limited success, she has a strong gag reflex so most comes back up!