Sentence examples for a best from inspiring English sources

"a best" is not a grammatically correct phrase in written English.
It is possible that you may have heard someone use this phrase in spoken English, but it is not appropriate to use in written communication. Instead, you can use "the best" or "one of the best" in a sentence to refer to something that is of superior quality or performance. Example: This restaurant is known for serving the best sushi in town.