The antonyms for the word "most sleepyhead" are "most alert," "most energetic," "most lively," "most wakeful," and "most active." These words indicate the opposite of being sleepy or drowsy. Someone who is most alert is highly attentive and conscious of their surroundings, while someone who is most energetic has a lot of vigor, enthusiasm, and vitality. The word "lively" suggests a high level of activity and excitement, while "wakeful" denotes the ability to stay awake and alert. Finally, the word "active" suggests a high level of physical or mental activity. Overall, these antonyms provide a contrast to the state of being sleepy and highlight the importance of being awake and alert.