Sour as vinegar is a commonly used simile to describe a sour taste or unpleasant experience. However, there are several other synonyms that can be used to describe a sour taste or experience. For instance, tart, acidic, bitter, acrid, sharp, and pungent are some of the synonyms that can be used to replace "sour as vinegar." All these words give an idea of an unpleasant taste, smell, or experience. When it comes to describing a sour personality, harsh, rude, bitter, unpleasant, and critical are some synonyms that can be used instead of "sour as vinegar." It is always good to have an extensive vocabulary to be able to communicate effectively.