Combine bread mix, egg, sour cream and 1/2 cup water in a mixing bowl. Stir until well moistened; spread in a lightly greased slow cooker.
Combine remaining water and other ingredients in a small saucepan; bring to a boil. Pour boiling mixture over batter in slow cooker. Cover and cook on high setting for 2 to 2 1/2 hours, until edges are golden.
Turn off slow cooker; let cake cool in slow cooker for about 30 minutes with lid ajar. When cool enough to handle, hold a large plate over top of slow cooker and invert to turn out cake.