The antonyms for the word "is sleepy" are words that describe the opposite state of sleepiness or drowsiness. These words include alert, awake, energetic, lively, vibrant, spirited, zesty, vivacious, perky, peppy, active, and refreshed. These words are associated with being wide awake, feeling energized, and having a clear mind. They convey a sense of liveliness and enthusiasm. Being alert and energized also improves motivation and productivity. Using antonyms for "is sleepy" gives a wider range of vocabulary to express the opposite of feeling tired and helps to convey the desired meaning more accurately.