(mainly because of the tamarind bars), I dropped by the 99 Cent Only Store.
Much if not most of the food you'll find here is junk or junk adjacent, but there are healthy options. You can prepare some tasty, nutritious, filling and very cheap meals if:
You have access to one of these stores (preferably with a car so you don't have to haul groceries on a bus);
You're flexible about your menu (inventories are driven by odd lots and approaching expiration dates so you don't know what you'll find);
You have time to shop and to cook;
You have the facilities to cook and store lots of food;
You like beans.
And potatoes (rice works too)
Hot sauce is your friend.
It's not obvious from the picture but this is a pretty big can.
I don't want to oversell the virtues of these stores or understate the challenges of maintaining a healthy diet near the poverty line, but too many of the people driving the hunger debate are coming from a Whole Foods sensibility and they inevitably screw up the discussion no matter how good their intentions may be.