Boil chicken in a saucepan of water for at least an hour. When soft, drain and allow to sit until cool enough to handle. On a cutting board, pull the chicken apart with two forks.
In a frying pan, heat the olive oil over medium high. Add the onion and cook for about 2 minutes. Add the garlic and cook for another minute. Add the shredded chicken, taco seasoning, cayenne pepper and water. Allow to cook until chicken is heated though and seasonings are combined.
On a plate, heat the tortillas for about 15-30 seconds, until soft. On each tortilla, spread beans, chicken, tomato, lettuce and grated cheese. Fold in half or roll up like a burrito.