I am not working currently as I am a carer for my elderly parents, so I eat lunch at home. I have set myself a budget of 1 pound a day for everything I eat, except for our main meal at night with my husband. It is quite possible to make 1 pound (British, 2 bucks approximately American) stretch, as I mostly live on snacks and fruit during the day. I mentally calculate the cost of everything as I go along - I know that's a bit sad, but it gives me a sense of satisfaction to stick within my budget. If I do go over one day, I cut back the next. It's a bit like a diet I suppose. I can make a big bowl of mashed potato with grated cheese mixed in for about 50p, and this covers lunch for 2 days. Then I can have a banana, an apple and a bag of crisps. There is no limit put on our evening meals, but we don't go mad! I am a great believer in looking after the pennies etc.
Not sad, I do the same thing only in American money. Try a bowl of black beans with a bit of shredded cheddar mixed in-- about 50 cents if you use dried beans and cook a bunch at once. (Not sure what that is in pence.)