I can get about 8000 calories of rice for $5 retail at a grocery store. Granted it costs money to cook it, and you'd want to mix in other ingredients for taste

I can get about 8000 calories of rice for $5 retail at a grocery store. Granted it costs money to cook it, and you'd want to mix in other ingredients for taste and nutrition. But 800 calories for 3 euros should be doable. For fast food, the Cheesy Bean and Rice burrito is still on the dollar menu at Taco Bell. 420 calories for $1, and a fairly complete lacto-vegetarian protein source. Buy one of those and a Fiesta Veggie Burrito ($2 for 570 calories) and you've got some vegetables too at almost $1000 calories. Make either of them Fresco and you replace the dairy with diced tomatoes, losing about 110 calories for the CBRB, and 145 calories for the FVB. Fresco only one and you still have greater than 800 calories. Maybe this isn't possible in Europe?