There are loads of great eating options. Nyaung U has the best choices, particularly along its well-known restaurant strip, Yarkinthar St. There are decent eateries along Khayea Pin St in New Bagan and outside Tharabar Gate in Old Bagan.
It’s worth planning ahead, as most temples in the Central Plain have little shade and nowhere to get lunch. The most convenient temple dining options are in and around Old Bagan.