Don't eat fruit or fruit juice for breakfast, they contain fast sugars so will increase your BG swiftly but also drop shortly after. I was told by my nurse that drinking fruit juuice is like drinking full fat coke! You want something with long-acting carbs, like wholemeal toast but avoid sugary toppings. (everyone is going nuts for avocado on toast right now!)
Porridge is really good if you can bring your self to try it. I like millet flake and flax seed porridge with seeds and flaked almonds and a little bit of cinnamon. it's much less lumpy than normal porridge and easier to digest.
I'm also a big fan of blueberry wheats cereal from Tesco - totally contradicts my assertion to avoid fruit for breakfast but the carbs are actually very low in sugar but good for long acting carbs, so is ideal for breakfast and taste scrummy too.
Eggs on toast will also be a winner everytime!
Good luck.