Shredded Chicken Tacos

Mix water and taco seasoning in a large bowl. Add tomato sauce, vinegar, garlic, oregano, cumin, and sugar; mix well.

Heat oil in a large skillet over medium-high heat. Add chicken and cook until golden brown, about 5 minutes per side. Add tomato sauce mixture and bring to a boil. Reduce heat to medium-low, cover, and simmer until chicken is no longer pink in the center and the juices run clear, about 20 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).

Remove chicken breasts from the pan and shred meat with 2 forks when cool enough to handle. Return shredded chicken to the pan with the tomato sauce. Cook and stir until chicken is coated with sauce and sauce reduces a bit, about 5 minutes.

Transfer chicken and sauce to a serving bowl and spoon onto taco shells.