Preheat oven to 350°F (175°C). Grease a 15x10-inch sheet pan and line with parchment paper if desired.

If using espresso powder, dissolve it into the warm water.

In a medium bowl, whisk together sugar, oil, warm espresso water, coffee, vanilla, and vinegar.

In a separate large bowl, whisk together flour, cocoa powder, baking soda, salt, and cinnamon.

Gradually fold the dry ingredients into the wet ingredients until just combined. Do not overmix.

Pour batter into the prepared sheet pan and smooth the top evenly.

Bake for 14–16 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.

Allow cake to cool completely in the pan on a wire rack.

To make the glaze, combine water, cocoa powder, and espresso powder in a small saucepan over low heat. Stir until smooth and slightly steaming.

Add sifted powdered sugar, vanilla, and salt. Stir until mostly smooth.

Remove from heat and stir in butter until melted and glossy.

Let glaze cool for 5–10 minutes until warm, but not hot.

Pour glaze evenly over the cooled cake and spread gently if needed. (Glaze has the potential to drip over the sides, so be cautious when pouring).

Let glaze set for 10–15 minutes before slicing and serving.