Greatbonsai is right on everything there. The syllabus is essentially the test.
But if you really need/want premade flashcard practice, there are flashcard apps that have a Cicerone Beer Server set in them. My classmates used Cram.
Based on my experience, the only portion of the BJCP Guidelines I would ignore is OG/FG, but even then, I've seen some people say that they've had questions reference those values.
There will be questions that specifically reference a beer with a specific range of SRM and ABV, with no additional information, and there will be some that require you to know specific points in the description that wouldn't apply to any other beers.
In addition, you'll see at least one long answer question requiring you to pretty much regurgitate all the information you can on a specific style, so knowing as much about as many styles as you can will be a massive help there.
I did three things to prepare for this, which I would use alongside trying as many varieties of the styles as I could.
I made a small laminated card that had style names and all the quantitative values and I would study as I drank beers, or whenever I had a few minutes. This gave me just something I could quickly check and put away.
I also found an app that allowed me to verify style information on the go, on Android it's at https://play.google.com/store/apps/details?id=io.github.rlshep.bjcp2015beerstyles
Then to quiz myself, I used a website that can quiz you or just give information. https://bjcp.thegremlyn.com