The bottle pictured below is a 32-ounce bottle, so I double the recipe.
from Clean House, Clean Planet by Karen Logan
2 Tbsp. vinegar
1 tsp. borax
1/4 c. liquid soap (castile soap)
10-15 drops essential oil, optional
Mix vinegar and borax in a 16-oz bottle. Fill the bottle with very hot water, leaving room for the liquid soap. Shake until the borax is dissolved. Add the liquid soap. Can add 10 to 15 drops of essential oil if desired.