Antonyms:
* Confidently: Expressing certainty and self-assurance.
* Boldly: With courage and determination.
* Bravely: Showing courage in the face of danger or difficulty.
* Proudly: With a sense of pride and satisfaction.
* Assertively: In a confident and forceful way.
Synonyms:
* Bashfully: Shyly and awkwardly.
* Timidly: Lacking confidence or courage.
* Embarrassedly: Feeling ashamed or awkward.
* Humbly: With a lack of pride or arrogance.
* Submissively: In a way that shows willingness to obey or submit.
The best choice for an antonym or synonym will depend on the specific context in which "sheepishly" is used.