Candidates can handle unexpected questions with poise during UPSC interviews by maintaining composure and adopting a calm mindset. Practicing active listening is vital; allowing the interviewer to complete their question before responding fosters clarity. Taking a moment to think before answering helps in formulating a coherent response. Candidates should remain honest and articulate, acknowledging when unsure about a topic while demonstrating a willingness to learn. Developing a knowledge base across diverse subjects assists candidates in navigating these situations, while practicing stress-management techniques can bolster their confidence.