I've been giving my daughter propranolol for almost 9 months now and I give it to her with her bottle. I make a bottle, shake it all up and then take the top off, put the nipple in her mouth and squirt in the meds and she sucks it down. Then I put the top back on and give her the rest of the bottle. Her meds aren't flavored either.
Good Luck, giving babies medicine is never easy.