I had no idea you could make febreze until I saw someone I knew had made it. She gave me the recipe, and then I did some research to find out where it originated from. While it's always hard to track things like this down, I found the recipe I received at FakeitFrugal.
1/8 cup Fabric Softener
2 tablespoons Baking Soda
Mix fabric softener and baking soda in a measuring cup until smooth.
Fill measuring cup with hot water and stir until well mixed.
Pour into spray bottle and fill the rest of the way with water.