I discovered that a choux bun filled with fresh cream didn't go too badly for me. In fact I posted the question on here as I couldn't understand how eating one of those (offset by a brisk walk) didn't affect me. Others told me that because choux pastry contains a lot of air, and because double cream has no carbs, a choux bun or eclair was the best pud for a type 2.
If it's proper cake you're after, I'd say none! My sister used to make sugar free lemon drizzle for my T2 son, but it still has carbs in so really that's off limits as well. This was before I became diabetic and discovered (from this lovely forum) that carbs were the main culprit.