Increase insulin activity - green tea, cocoa, cherries
Lower blood sugar level - Guava, buckwheat, cinnamon
All diabetics are a bit different in what we can eat and still keep our blood glucose in target range. In general most of us find we need to eliminate sugar and greatly reduce carbohydrate intake especially things like white bread, cereal rice and pasta.
The best way to know what works for YOU is to try a certain food and test your blood glucose two hours after eating and make sure you stay within target. If a certain food spikes you up say over 140 you might try a lesser amount of that food or just eliminate it from your diet. It is not really possible to make a list of foods to eat and not eat because we are all different. But a diet of protein and lots of fresh vegies, small amounts of fruit and small amounts of carbs should do best.