Everyone Deserves Their Own Birthday Cake

I've met many people with a variety of food allergies. This is often the first recipe I give someone when I learn they have a child with a food allergy. All of them love this cake and I've had nothing but glowing feedback. It is simple to make and is free of most common food allergens.
I got this recipe from a freebie "Cowboy Cooking" cookbook that was packaged with Marlboro cigarettes. I didn't smoke them, but I had a friend who worked at a liquor store who gave it to me from a carton opened for "single pack" sales.

Stir Crazy Cake2 ½ cups wheat-free flour blend
1 ½ cups sugar
1/2 cups cocoa
2 teaspoons baking soda
½ teaspoon salt
2/3 cup cooking oil
2 tablespoons vinegar
1 tablespoon vanilla
2 cups cold coffee (or cold water)
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¼ cup sugar
½ teaspoon cinnamon

Put flour, 1 ½ cup sugar, cocoa, soda and salt into ungreased 13x9x2-inch baking pan. Stir with a fork to mix; form 3 wells in mixture. Pour oil in one well, vinegar in one and vanilla in one. Pour cold coffee over all ingredients and stir with fork until well mixed (do not beat). Combine remaining sugar and cinnamon; sprinkle over batter. Bake in 350 degree Fahrenheit oven for 35-40 minutes.