Mesh: Default Cube with single loop cut Ctrl+r and the top Face scaled. With a Subdivision Surface modifier and Smooth shading. Feel free to make this mesh a bit less "perfect".
Looks complicated but it can be broken down into simple areas. The Far left Object Info and ColorRamp are just so any duplicated meshes get a random colour.
This leads into the base Diffuse BSDF which is mixed with a bit of transparency using the Fresnel as the factor.
Then the top set of nodes use the Generated texture coordinates through a Noise Texture (with quite a large Scale) into a constriction ColorRamp. If you play with the colour stops you change the pattern and distribution of "sugar". We then use a Bump node to create a Normal Displacement to give the "sugar" depth.
Attempt 2: Particle Emitter
Add another Cube (I have named mine "sugar") and setup the particle emitter settings for your sweet mesh.
I am opting to use an emitter not hair. The End is set to 1.0 so the particles are all created instantly. Render Object is set to "sugar". Children is Simple and size set to 0.25. Render is set to 10 but you can tweak to increase the total rendered amount.
FYI I added an Emitter Shader to brighten them up this time.
There is lots of room for improvement but I hope this gets you started.