A tortilla bread recipe calls for 3/4 cup milk, is it okay to use yogurt which is thinned by water?      Flour 2 cups    Baking powder 1 and 1/2 tsp      Salt  1/2 tsp   Oil 2 tbsp   Warm milk 3/4 cup   Many other recipes call for water instead, but I believe milk makes the bread softer and affect the texture. That's why I'd use yogurt.  
Yogurt will work just fine. It will even give you some nice extra flavor.  Unless it is greek yogurt you don't need to thin it at all. Greek yogurt has some water drained off but normal yogurt has the same water content as the milk it was made from.  In some recipes you might have to thin it to get the right consistency to work with but in the case of flour doughs you can just mix it into the dough straight.  