Heat oil in large skillet on medium-high heat. Add chicken; cook and stir 10 minutes or until browned. Add onion; cook and stir 5 minutes or until softened.
Stir in tomatoes, water and seasonings. Bring to boil, stirring occasionally. Reduce heat to low; cover and simmer 3 minutes or until heated through.
Stir in spinach; cook 2 minutes or until spinach begins to wilt.