Hi Sarah,
The full fat varieties have the least amount of carbs in them. Berries such as blueberries, raspberries and blackberries dont have many carbs in them - as far as I can tell berries are the only fruit that dont affect my BGs.
You could mix the yoghurt and berries together and add a bit of granulated sweetener (if too sharp) otherwise crush them into the yoghurt. I find Greek yoghurt is the best, but I could wolf down a whole large tub of it in one go!