Preheat oven to 190 C (gasmark 5).
Grease an 18cm cake tin, line it, and grease the lining. A spring-form tin is best, or one with a removable bottom.
Dissolve the coffee granules in the milk.
To make the topping, mix together the flour, sgtuar and cinnamon. Rub in the margarine until the mixture resembles breadcrumbs. Put aside until later.
Sift the flour and bicarbonate of soda into a bowl. Stir in the sugar.
Combine the egg, yoghurt, syrup and melted margarine in a jug. Add the coffee and milk mixture, and mix well.
Add the liquid ingredients to the flour mixture, and mix until combined.
Spoon the mixture into the tin. Sprinkle the topping over the top.
Bake for 25-30 minutes, or until a knife inserted into the centre of the cake comes out clean.
Cool on a wire rack for 5 minutes, then remove the cake from the tin - do not turn it upside down. Serve warm or cold.