Pack a quart size glass jar tightly with leftover citrus peels, and then fill jar to the top with vinegar. Close and set in a sunny spot to infuse for at least two weeks.
Strain the vinegar, discard the peels, and store the vinegar in a glass jar in a dark, cool spot.
To make all-purpose cleaner, pour 1/2 cup of the vinegar into a spray bottle. Add in 2 cups water, 1 teaspoon castile soap, and 20 drops lemon essential oil, if using. Screw on lid and shake well.
To use: shake the mixture well, and then spray onto surface and wipe clean with a damp cloth.
Notes
Yes, this still smells like vinegar! But only for a second. The vinegar scent quickly dissipates and you are left with a fresh citrus scent.
Do NOT use this cleaner on natural stone countertops or tiles. Extended use of vinegar can cause pitting in natural stone.
UPDATE: A commenter reminded me that the vinegar in this recipe would cancel out the Castile soap—and that's true. Feel free to leave out the Castille soap and you'll still have a wonderful vinegar-based cleaner.