Will sipping through straw enlarge my masseters?

Hi and thanks for your interesting question. No evidence that sipping through even a very long straw!!! will achieve muscle bulk. Try chewing gum, as this is more likely to help increase bulk of your massetters

Hi and thanks for posting. Pursing your lips to sip through a straw uses the orbicularis oris muscle.  This muscles sits around the upper and lower lip in a ring like manner. The masseter muscle is used to clench your teeth, bite down and chew. You can feel the masseter's location by placing your hand on the sides of the face and jawline and bite down. I would not worry about enlarging any of these muscles from normal daily function.