Wash everything well. Rinse apples, spinach, and cucumber under cool water.
Pat dry.
Prep the produce. Core the apples if you like (or leave cores if your juicer handles them). Peel the lemon. Cut cucumber into chunks.
If using ginger, peel it.
If using a juicer: Juice spinach first, then cucumber, apple, lemon, and ginger. Stir the juice to combine.
If using a blender: Add spinach, cucumber, apple chunks, peeled lemon, and ginger with 1/2 to 3/4 cup cold water. Blend until very smooth, 45–60 seconds.
Strain (blender method): Pour the mixture through a fine-mesh sieve or nut milk bag into a bowl or pitcher.
Press or squeeze to extract the juice.
Taste and adjust. For extra sweetness, add another half apple. If you want more zing, add a splash of lemon.
Serve cold. Pour over ice or chill for 10–15 minutes. Stir before serving.