Formal:
* Me ke aloha nui: This literally means "with great love" and can be used as a formal closing in a letter or email.
* Aloha nui: This means "much love" and can be used as a more casual closing.
Informal:
* Mahalo nui loa: This means "thank you very much" and can be used as a closing in a casual note or message.
* Aloha: This simply means "hello" or "goodbye" but can also be used as a way to express affection or gratitude.
Adding more context:
* Me ke aloha a me ka mahalo: This means "with love and thanks" and can be used as a more comprehensive closing.
Ultimately, the best way to say "Sincerely" in Hawaiian is to choose the option that best fits the tone and formality of your message.