Pour 1/2 cup white vinegar and 1/4 cup rubbing alcohol into a spray bottle via a funnel. Rinse the cup.
Mix one tablespoon of cold water and cornstarch in a cup, whisk until smooth, then funnel into the spray bottle.
Pour two cups of cold or distilled water into the spray bottle. For a citrusy scent, add lemon essential oil drops.
Secure the cap, shake homemade cleaner, clean the glass with a microfibre cloth, and dry for a streak-free shine.