In a friends-only voicepost yesterday, I was commissioned to engage in an experiment: to substitute some juice from the drained blueberries in a Betty Crocker muffin mix for a bit of the water. Below is a report on the experiment.
Truthfully, I nearly forgot to do it. I put in the water and then opened the blueberry can and thought, "Oh, the juice! What to do...?" But I am nice and creative--or perhaps daring.
I measured the water that I drained. 3/4 cup--precisely as much juice as the amount of water called for in the recipe on the box. I don't know whether that is coincidental. If it could be substituted successfully, the only problem would be that you would suposedly have blue muffins according to the FAQ on the Betty Crocker site. I, unfortunately, cannot report accurately on that aspect of the experiment.
In light of my memory lapse, I improvised. I added 1/4 cup of juice and 1/4 cup of flour, checking the consistency of the dough as I went along so that it stayed the same. The intended outcome was that I would get bigger, more flavorful muffins.