The Varsity Sweet Shop at 200 19th Ave was the site of the invention of the bendy straw in the 1930s. Wikipedia explains this invention in the biography of its inventor, Joseph Friedman:
While sitting in his younger brother Albert's fountain parlor, the Varsity Sweet Shop in San Francisco, Friedman observed his young daughter Judith at the counter, struggling to drink out of a straight straw. He took a paper straight straw, inserted a screw and using dental floss, he wrapped the paper into the screw threads, creating corrugations. After removing the screw, the altered paper straw would bend conveniently over the edge of the glass, allowing small children to better reach their beverages.
None of the bendy straw articles on the web say where the Varsity Sweet Shop was located, but you can find its address in old phone and address directories hosted by a SF genealogy website. Here's a listing in 1938 and another one in 1940.
This location is currently New Shining Cleaners.