I write this piece for that hungry traveller connecting through terminal 3 on a United flight in San Fancisco International Airport (SFO). Go directly to Andale Mexican restraurant and order one of their burritos.
My family and I usually fly through SFO at least once a year on United. Even on a 20 minute layover, we ALWAYS stop at Andale Mexican Resturant. If I fly home through SFO, it is not unusal for my daughter to ask me to pick up a burrito for her before I take off.

The food is flavorful and worth the slightly longer than normal wait. Prices are moderate compared to normal airport food. Beverages are marked up pretty well at this place, but one comes to expect that at an airport. They have a veggie burrito that is absolutely amazing.
There is also a little bakery next to Andale that sells great sourdough loafs of bread. That is also a nice treat.
Safe Journey.