When I know my bm supply is running low, I intro 2 feeds of fm to my little one. I did it slowly as in, one feed bm, n the next feed fm. He cried when he noticed the difference n tried to push the bottle away. I let him be a little more hungry n fed him fm again n this time, he took it slowly.
Children r v smart. U just have to play, distract n feed at the same time. Sing song or read a book. They will get used to the taste.