First We Feast reader Juan Cisneros made this great comic explaining why astronauts eat tortillas instead of bread in space. Mexican astronaut and scientist Rodolfo Neri Vela was the first requesting them for a mission back in 1985. From that moment it became a staple of the astronauts' diet.
They use Taco Bell's tortillas that can last up to one year with no degradation. This video shows NASA's Chris Hadfield and chef Traci Des Jardins getting creative and making a burrito in space: