Formats that work best for memorizing data-heavy subjects for UPSC exams include flashcards, mind maps, and visual aids. Flashcards facilitate active recall and spaced repetition, essential for memorizing facts and figures. Mind maps allow students to organize information visually, helping to identify connections and relationships between topics. Visual aids, such as infographics and charts, can enhance comprehension and retention of complex data. Additionally, incorporating summarization techniques, like creating concise notes from chapters, can facilitate quicker revision. Utilizing these formats enables aspirants to manage large volumes of information efficiently.