Before Security, there are two outlets serving beer, wine and South African plates. After Security, you can find a number of options including a sit-down café-bar and a pizza diner. For a great view of the runway while you eat, head to Mugg & Bean for bottomless coffee and a decent menu including kids and vegetarian options.
For a great view of the airport, check out the public viewing deck on the 4th floor.
Follow the signs from the international Arrivals and Departures escalators.