In a large bowl, combine the flour, sugar, cocoa, baking soda, chocolate chips and salt. Toss to combine. In a medium bowl, whisk together the eggs, sour cream, water (or juice), milk, oil and vanilla. Make a well in the center of the dry ingredients and stir in the wet mixture, stirring just until moistened (a few dry streaks and lumps are fine).
Line muffins cups with paper liners and fill the cups 1/2 to 2/3 full. Bake for 16-18 minutes, until a toothpick inserted in the center of a muffin comes out clean. Remove the muffins to a wire rack to let cool completely.
Quantity: this recipe makes more than 24 muffins. Because I only have two regular-sized muffins pans and was impatient, I made the rest of the batter into 16 mini muffins. You could easily make all regular-sized muffins if you want. Juice: also, I had some all-natural plum juice in the refrigerator and subbed that in for the water. The taste was unnoticeable but was a little boost in fruit and fiber. I think the water would work just as well, but if you have plum juice just sitting around, throw it in!