Just . Don't . Eat . Crap.
Not trying to go smartass on you but I go somewhere and there's no actual food, I don't eat. You can always chow down on the good stuff when you get home or simply turn it into an unplanned fast.
No suggestions on the cake/muffin/weekend food thing. I don't eat the first two at all and my weekend food is the same as my weekday food; lots of meat, veggies and a little fruit & dairy.