Zonking out is an informal term that means falling asleep or being too tired to concentrate. Its antonyms could include being alert, awake, attentive, focused, energized, stimulated, and primed. When one zonks out, they become inactive and unresponsive, but the opposite of that would be being active, reactive, enthusiastic, and engaged. To stay awake and be productive, you could counter zonking out by drinking caffeine, practicing mindfulness or yoga, exercising, reading, or listening to upbeat music. In short, staying active, alert, and mindful can help avoid zonking out and maintain high energy and productivity levels.