Not the easiest question to answer without knowing your situation, existing BG levels, how you react to different foods etc. If you don't yet know, lunch is a good time to begin your learning process.
I got myself a meter and knew that sugary foods were off the menu. What I learned after getting a meter was that things like white bread were just as bad as sugary foods. I could however, eat pumpernickel and tortilla wraps seemed to be OK too, along with things like ryvita.
Any of these things go well with tinned fish like mackerel (in a spicy tomato sauce) or tuna, with mixed salad. Tuna chunks with tomato, cripsy lettuce, cucumber, spring onions, radishes etc in a tortilla wrap make a nice lunch. Sometimes I will have an olive and feta cheese salad with just a drizzle of balsamico. If I want something more hearty, pumpernickel with sliced cheese and meats, say pepper salami or smoked ham plus a tomato and red onion salad. I also like herrings in various ways, the rollmop herring being easy to serve up. Occasionally a boiled egg goes with the salad and sometimes it is a pickled boiled egg. Pickled onions and gerkhins are too, favourites.
As my control improved, I started to eat rye bread, but proper rye bread from trusted sources. Much so called ryebread has only a little rye and a lot of white flour. I later learned that I could tolerate wholegrain spelt, an early historical variety of wheat. Such breads are heavy because they don't rise well. Anything which is light and fluffy probably has a lot of highly refined flour. I have to eat the bricks but I do like them. Not everyone does. They are also great if you have a stew or heavy soup.
Test how you react to foods which have complex carbs. Eat just a little to begin with and see how you get on. If something spikes you too much, leave it for a few weeks but, as your BG levels improve, for it takes time to do so, come back and give it another go.
