First, combine water and espresso in a small bowl. In a stand mixer, beat butter and sugars. Add eggs, one at a time, followed by vanilla and espresso/water. In a separate bowl, combine the flour, baking soda, cream of tartar, salt and cocoa powder.
Slowly add in the dry ingredients, scraping down the sides of the bowl as needed.
Refrigerate dough for 2-4 hours, until firm.
When ready to bake, preheat the oven to 350F and line two baking sheets with parchment paper.
Combine cinnamon and sugar in a small bowl, and roll 1 inch balls into the mixture before placing on the cookie sheet.
Bake for 10-12 minutes until cracks appear on the surface of the cookies.
Let cool, and store in an airtight container for up to a week.
Recipe by pretty plain janes at https://prettyplainjanes.com/2015/01/07/espresso-snickerdoodles/