Also, you can make your own brown sugar
Have you ever started to bake, only to realize that the recipe calls for brown sugar and you don't have any on hand? So you start scrambling around, trying to find a brown sugar substitute somewhere in your kitchen cabinets? Well, I've got some great news for you. The easiest brown sugar substitute is, in fact, white sugar. Yes, simply swap in white sugar where a recipe calls for brown sugar. If you need one cup of brown sugar, use one cup of white sugar. According to the folks at Better Homes & Gardens, your recipe will still work—though it might not taste the same.
The reason this baking hack only works some of the time is because there is a big difference between brown and white sugar. As professionally trained pastry chef Stella Parks wrote in Serious Eats, "White and brown sugars can be swapped without fuss in any recipe where the chemistry isn't important. So....not very many recipes, to be honest." There are dozens of different chemical reactions that take place when you're cooking or baking, and the different types of sugar can have different reactions than what the recipe creators originally intended. That means there'll be changes in the texture of the dish if you're swapping sugars, even if it works in a moment of crisis.
That's why when a recipe calls for brown sugar, it's best to use real brown sugar. And if you still don't have brown sugar but feel bad about replacing it with granulated sugar, you can always make your own brown sugar using white sugar. That's because brown sugar is just regular old granulated sugar that's been processed with molasses, so all you have to do to make brown sugar is add a couple tablespoons of molasses to white sugar. You can either dump the ingredients into a food processor or blender to get the right, sticky consistency, or you can just mix with a spoon.
If you don't have molasses (which isn't weird, because how many people actually have molasses in their cabinets?), you can also use agave nectar or maple syrup to make brown sugar at home. Use about the same proportions: 2 tablespoons of liquid to 1 cup of granulated sugar. Or you could just get brown sugar and store it properly so it doesn't get all hardened—but that would probably be too easy.