Aspirants can prepare for unexpected changes in the UPSC exam by adopting a flexible study plan. This includes regularly updating their knowledge based on current events and trends affecting the exam. Practicing sample papers and previous years' questions can help aspirants become accustomed to different question formats. Additionally, attending coaching classes or study groups can provide diverse insights and perspectives on various topics. Keeping abreast with UPSC notifications and adhering to a rigorous review schedule can further ensure readiness for any changes in the exam structure.