In Wallonia CPAS may offer options for receiving free or discounted food, depending on the commune. It is encouraged to visit and ask at your commune about taking advantage of the services they offer, particularly in regards to specific things like potentially receiving free nappies or other supplies.
In Flanders OCMW depending on the commune provides options for free or discounted food.
"Resto du Cœur - L’Autre Table," offers complete, healthy and balanced meals at lunchtime at affordable prices to those in difficult situations, as well as breakfasts on Mondays and Fridays. http://www.restosducoeur.be/nl/
The Social Protestant Center in Brussels has a restaurant for cheap meals everyday at lunchtime. (http://www.csp-psc.be/services/babbelkot)