Anything which isn't refined or processed. Porridge is ideal.
You can get some good quality 0 sugar processed/refined granola too - it is more expensive though, but worth it for your health.
The problem is, even all those "healthy" cereals, have lots of sugar in them. Even Bran flakes and wheatabix etc....
Ultimately, if you want to stay fuller longer, a mixture of low GI carbs and protein will sort you out.