I have taken this exact routing down to MIA UA 855 (Seat 8F) on two occasions in May.

Yes there is food in C. It was a sandwich on a hot rye roll. It had the full collection of meats (turkey, ham, salami, and a cheese I couldn't quite ID ) It also had a Walker Shortbread for the dessert, which is still in my bag. There was also a salad with lettuce and fruit.

The return flight out of MIA had the exact same meal in F. Out of PBI, which I believe is a morning departure, has the usual UAL breakfast.

Hope this helps.

Nathan