To a mixing bowl, add dry ingredients like flour, baking powder, salt, instant coffee powder, cacao powder and mix to combine. Keep aside.
To a glass jar or cup add soy milk and warm it in microwave for 30 seconds. Add apple cider vinegar to warm soy milk and leave it aside for 10 mins. This makes soy milk to curdle and act like buttermilk.
In meantime, prepare baking tray by spraying with cooking oil and lining parchment paper.
After 10 mins, when you see soy milk curdle, add sugar, vanilla extract, vegetable oil to milk and mix to combine.
Now add wet ingredients to dry and mix to combine. Transfer cake batter to parchment lined baking tray and tap lightly on countertop to get rid of any air bubbles.
Bake at 350F for 25-30 mins. Bake till toothpick inserted at center of cake comes out clean.
Let cake cool completely or overnight in refrigerator before adding frosting.