To drop a few pieces or drops of something over a surface. (Cambridge Dictionary)
If you sprinkle a thing with something such as a liquid or powder, you scatter the liquid or powder over it. (Collins Dictionary)
If something is sprinkled with particular things, it has a few of them throughout it and they are far apart from each other. (Collins Dictionary)
Cover (an object or surface) with small drops or particles of a substance. (Oxford Dictionaries)
Scatter or pour (small drops or particles of a substance) over an object or surface. (Oxford Dictionaries)
To scatter in drops or particles. (Merriam – Webster)
Rainbow sprinkle sugar cookies.