Latin Review
not AP-specific, but good nonetheless
This practice is just general latin review at various levels for the National Latin Exam, but could help you refresh your memory on grammar bits:
Same is true for the SAT Latin subject test - it's not the same literature as the AP exam , but it has free practice with the grammar:
https://sat.collegeboard.org/practice/sat-subject-test-preparation/latin
Also, for declension-specific practice, you can help yourself remember the endings for nouns - gender - number - case at: