I've made a vector graphic of a donut. See . But I'd like to add an effect of a glaze where the glaze has differing opacity throughout. How can I achieve this?!
You could use a Gradient Mesh.
With Illustrator CS5 or newer you can apply transparency to gradient mesh points. Then you would need a clipping mask to remove the "glaze" from over the hole in the donut.
I've used a gradient mesh for the basic shape and transparency of the glaze. Then I added a clipping mask to the mesh to remove the "hole" of the donut. I then added some simple arched shapes with a black to white gradient fill applied tot hem, changed the blend mode to "screen" (only works in RGB mode) and placed them around the glaze edge to add a bit more depth.
Sprinkles are just for fun (they are symbols).