Cooking spray is super convenient to have around, but it can be expensive compared to regular old oil, and sometimes comes with some nasty sounding additives like dimethylpolysiloxane and dimethyl silicone.
All you have to do is mix one part cooking oil with five parts water and pour it in a spray bottle with a mister setting (for more pan coverage).
Make sure you're using filtered, distilled, or boiled water and a clean bottle to prevent bacteria growth. Store your spray in a dark, cool place, or in the fridge if you're concerned about bacteria.
You can also add lecithin to make nonstick spray. Most store-bought cooking sprays contain soy lecithin, an emulsifier that can come from both plants and animals. You can find it at your local health food store, but if most of your cookware is nonstick, it's probably best to skip it since lecithin can cause a sticky buildup on pans.
Have you tried making your own cooking spray? Let us know how it compares to the store-bought stuff in the comments.