What is a good replacement for 1/4 tsp mild rice vinegar?

I'd probably use apple cider vinegar or lemon juice. But, chocolate might cover up the flavor of even white wine vinegar. I've made a vegan chocolate cake with white wine vinegar and you really couldn't taste the vinegar at all.

In this case, I don't think I'd sub any vinegar other than Champagne vinegar. It's very mild.

Rice is gluten free. The rice wine vinegar shouldn't be a problem unless its not in your pantry!

It might be in there to add an acid to the baking soda to help the muffins rise. In that case, I'd use the same amount of lemon juice or white or apple cider vinegar. (Rice vinegar is probably used because it has such a mild taste, but you probably won't taste 1/4 teaspoon.)

It is suck a small amount I would just leave it out but maybe substitute white wine vinegar.