Sauraha's main street feeds tourists and does it competently; the food actually worth chasing here is Tharu, and it is not on those menus.
Sauraha's main street
A single strip of garden restaurants and rooftop kitchens running back from the river, doing dal bhat, momo and a broad tourist menu. It is walkable end to end in ten minutes and largely done by 10pm.
Tharu food — dhikri, ghonghi, bagiya
The Terai's indigenous cooking: dhikri are steamed rice-flour dumplings shaped as birds and fish and eaten with chutney; ghonghi is a river-snail gravy served with rice, made around the end of the monsoon; sidhara mixes taro stem with dried fish and is an acquired taste. Ask a homestay or a Tharu kitchen — the tourist strip won't have it.
Dal bhat, twice a day
Rice, lentils, a vegetable and pickle, with refills of rice and dal included — it is what the guides eat between shifts and the best-value meal in Sauraha by a distance. Order it and you will not be hungry again for six hours.
The Bharatpur run
Twenty kilometres west, Bharatpur and Narayangadh are where the district actually eats and shops: proper supermarkets, sweet shops and non-tourist thali houses. Worth a half-day if you are staying more than three or four nights.