I had the same problem with Lolly hun, it took her a long while to work out how to suck from a beaker too and she wouldn't drink milk from it at all

Eventually i got her to swop over to a beaker. tbh we were lucky in a way because she got a tummy bug (not related to bottle) and i told her it was the bottle that had made her sick. We chucked them in the bin together then and she drank from a beaker for all her drinks from then on, she was just coming up for 2 at the time. I hope you manage to get your
LO onto a beaker for his milk soon hun. The cow beaker is a great idea! Xx