Image courtesy magazineart.org
This might be the weirdest thing I ever posted, but it works. One day when I burned a batch of waffles, I noticed that it cleaned out my waffle iron quite nicely. But as I generally try not to burn waffles, since we'd rather eat them, I came up with this.
It's just a waffle recipe stripped down to the basics, using only the cheapest ingredients. This will not taste good. It's not for eating; it's for cleaning. Leaving out the milk, sugar, and eggs helps it not to brown and burn (and stink) too much. I also included plenty of oil to be sure that it will come off nicely in the end (and hopefully leave a nice slippery coating on your iron for next time).
This works for me. It may or may not work for you. Just thought I'd say that.
Waffle iron cleaner
2/3 cup flour
1/4 teaspoon baking soda
2/3 cup water
1 teaspoon vinegar
3 tablespoons oil
Heat waffle iron. Fill with batter—fill it full, because it cleans only where it touches. Cook for about three times your usual time (about ten minutes total for me).