Preheat the oven to 180C/356F. Lightly grease and line a 20cm cake tin.
Combine the flour, sugar, baking powder, baking soda and salt in a large mixing bowl. Whisk to combine.
In a smaller mixing bowl, whisk together the milk and yoghurt, then add the vinegar. The mixture should thicken almost straight away.
Add the yoghurt mix, eggs and oil to the flour and whisk until completely smooth. Add the optional flavourings here, if you're using them.
Whisk in the sprinkles, then transfer the batter into the greased cake tin. Bake for 30-35 minutes or until the top is golden brown and a skewer comes out clean. The centre middle is the last to cook, so make sure you check it is done.
Once cooked, allow to cool for 5-10 minutes before gently removing from the cake tin. You might need to run a knife around it first. Take the baking paper off and set on a cake rack to cool. Allow to cool completely if you’re icing.
The cake keeps well for 2-3 days in an airtight container.