The phrase "bunks out" typically means to go to bed or to call it a night. The antonyms for this phrase would be to stay up, not sleep, or to be awake. Alternatively, if you're looking for the opposite activity, you could try going for a walk or engaging in some other stimulating activity. It's important to note that different contexts may require different antonyms, as a person could "bunk out" of a party, meaning they decided to leave early, in which case the appropriate antonyms would be to stay longer or to remain at the event.