The cost of alimentation in Warsaw, similar to other cities, largely depends on your eating habits, so to speak. If you cook your own meals then the cost should range between 360-500 PLN (85-125 EUR). However, if you prefer to eat out, you will spend at least 750 PLN (185 EUR) on food alone.
A meal in fast-food restaurants or cheap cafeterias (called bar mleczny in Poland) costs between 8-20 PLN (2-5 EUR). If you choose something more fancy, you may need to pay at least 60 PLN (15 EUR) per person. Obviously, the better standard is, the higher are the prices.