I picked one up while in Vermont for 99 cents.
The best thing about Dunkin's Blueberry Cake Donut is that they offer one at all; none of the donut shops in my neighborhood offer them.
Sadly, it's about as mediocre a blueberry donut that I've ever eaten. That's not to say it's bad. It's still a donut after all, but it's very unnoteworthy.
It wasn't very fresh. I'd guess at least a day old, but it still managed to exhibit a slight crust. I'm guessing the glaze helps a bit.
Overall, Dunkin' Donut's Blueberry Cake Donut is decent as far as donuts go and just a little better than packaged store-bought donuts.
Nutritional Info - Dunkin' Donuts Blueberry Cake Donut
Calories - 340 (from Fat - 150)
Fat - 17g (Saturated Fat - 8g)
Sodium - 570mg
Carbs - 44g (Sugar - 21g)
Protein - 4g