Hi. Anything that says 'diet' on it is likely to be a 'no'. It's likely to add sugar or other sweeteners to be 'low fat'. Your best bet is a greek yoghurt, the only ingredients you want are milk and culture.
I abandoned cereal altogether. If you don't like milk, why would you like a product that is basically sour milk ? Any yoghurt that is sweet, is bad. I have a cooked breakfast, like mushrooms, eggs, proscuitto. I tend to have a lighter lunch, but you could have toast with avocado or similar for breakfast if you prefer. What cereal are you having ? There's almost none that are sugar free. I looked forever for a sugar free muesli, but ended up just giving up on trying to eat it.