Question: What did Sister Mary Patrick mean when she said "you don't have to bite the donut to know it's sweet"? I believe this was in the scene when she was teaching her class when Deloris was looking for hers.
Answer: You don't need to learn about sex to know what it is about.
Answer: Sister Mary Patrick is being challenged by Sondra, one of her students, who says, "you can't answer any questions about... Sex." The sister's reply is, "oh, don't be so sure - you don't have to bite the donut to know it's sweet." She offers this as an analogy, in order to posit that one doesn't have to have engaged in sex acts to know what sex is all about, or that it may be enjoyable even when it isn't necessarily good for you.
Michael Albert