Is there something I can substitute for the yogurt or sour cream in the cake mix enxtender recipe here in CC? Thanks in advance.

You could probably substitute buttermilk.. You wouldn't want to put as much as it calls for yogurt, but probably about 3/4 c instead of a full cup. The sour cream is to make it really moist and buttermilk usually has the same effect, but I love to use sour cream in my recipes.