I would go through some MMI practice questions, there are a bunch available online. It helps to get used to the format and it helps you get comfortable with approaching difficult ethical situations. Honestly all of the ones I found online were more difficult than the ones that popped up in my MMI, but it did help to browse through questions and topics and see "oh yeah I could get a question about alternative, how would I answer that?" Looking through the questions can help you become more concise too because you are already familiar with the format and content, which is important so the interviewer can ask you follow up questions.
I found this site really helpful for reviewing bioethics topics. I can't say in the interview I thought back to it, but it definitely has thought-provoking and helpful information.
https://depts.washington.edu/bioethx/topics/
Finally, be prepared to answer any of the "classic interview questions". If you've prepared for normal interviews before, you should be fine with the "classic interview questions" if they were to show up on the MMI.