Mix together the tapioca flour, mozzarella, cojita, baking powder, and salt in a large bowl.
Whisk the eggs together. Add to the bowl with melted butter, milk, and water. Mix together until a dough forms. Add more water, 1 tablespoon at a time, if needed.
Roll the dough into 30 balls and place them on a sheet pan. Try to keep them roughly the same size. Place them in the refrigerater for at least 30 minutes.
Preheat oven to 400F. Bake for 10 - 15 minutes, or until brown specks form on top (that's the cheese!). Enjoy immediately; careful, they'll be hot!