Mix cola and ketchup in a deep skillet. Put in chicken. Bring mixture to a boil. Turn down to a simmer. Simmer chicken 5 minutes. Then turn over to the other side and simmer 5 more minutes or until cooked through.
Remove chicken from pan and leave mixture cooking to reduce to a sauce while you shred your chicken. (The easiest way is with 2 forks.)
Put your chicken back in the mixture. Mix and serve on buns.