This are super cute ideas for Halloween :D

Royal icing is super easy if you buy the powder from a cake decorating or party store. Just add powdered sugar. You can also get the food dyes at the same store, and they are much (much) stronger than the grocery store kinds, so you'll get eyes that look just like the above.

Barring that, maybe a tiny blob of marshmallow fluff and a small black candy, like a punch out of a piece of licorice? Or (red would be cool) a cinnamon candy like a gingerbread guy button.

Have fun!

You could do pressed sugar. Just mix water drop by drop into plain sugar til it looks like clumpy slightly wet sand. Pat it how thick you want and cut with cookie cutters or roll/mush into eye shapes. Let it dry.

I personally would do royal icing. Itll look nicest. If yo want a solid look, you could mix up a bit of black or any color and drop a small drop in the center of the still wet white royal icing for a flush colored eye. If you got really creative you could do a drop of blue/green/brown and hen a drop of black and it would look like a real iris/pupil.

Not do-it-yourself, but I have been using Haribo Raspberries. They make really good bug eyes, the little spheres on the candy mimics the facets on bug eyes. Stick them on cookies when they are hot out of the oven and they adhere nicely.