As cheaply as human possible! My go to staples were: Top Ramen, eggs, cheese sandwiches, canned Tuna, and the dollar menu at Wendy’s (if I was splurging). As a hunter and a fisherman I all ways had a freezer full of wild game and fish, and those were my protein sources.
Once is a blue moon I would spring for a local breakfast buffet place ($2.99), and my goal was a whole days worth of food from that one meal because $3.00 was extravagant.