“Nearly” fits well with “weren’t” to express that the bananas were not quite ripe enough, which matches the intended meaning. So the completed sentence is: "The bananas weren’t nearly ripe enough to use today."

“Almost” is typically used in affirmative statements (e.g., The bananas are almost ripe), but in negative statements, it can sound awkward or ambiguous. “Scarcely” means “barely” or “only just,” and is usually used in a slightly different context. It also sounds awkward with “weren’t” (double negation). “Hardly” also implies “barely,” but like “scarcely,” when used with a negative verb like “weren’t,” it becomes a double negative, which is grammatically incorrect in standard English.