Preheat the oven to 365°F and cover a round or square cake pan with parchment paper (I have not tried a bread pan, but muffins work if you want mini cakes).
In a bowl mix the dry ingredients, then make a well in the middle and pour the vinegar, vanilla extract, and oil.
180 g all-purpose or whole-wheat flour, 200 g sugar, 1 teaspoon baking soda, 1 pinch salt, 1 tbsp white wine vinegar, 1 tsp vanilla extract, 5 tbsp sunflower or peanut oil, 3.5 tbsp unsweetened cocoa
Pour in the water and mix well with a spoon, until a smooth and thick batter, comes together. Get rid of all lumps by stirring thoroughly.
1 cup warm water
Transfer the cake batter to the previously prepared pan, and cook in the preheated oven for 35 minutes. If you are not sure whether the cake is done, test it with a toothpick, but do not over-bake it, as it might turn out too dry.