Place your canning jars, lids and rings in your hot water bath canner to boil and sterilize. Or, alternatively, place them in a 200 degree F oven until ready to fill.
Shred your kohlrabi - using your food processor; or, quarter the kohlrabi and place in a high powered blender (Vitamin) for shredding. Each large kohlrabi should equal one half pint (more or less).
In a large pot, combine the kohlrabi, apple cider vinegar, garlic, sugar, salt and pepper. Bring pot to high heat and allow the mixture to boil; cook for 3-4 minutes. Kohlrabi should release some of its liquid and soften up.
Pack the kohlrabi in your half pint jars; ladle remaining liquid over to cover, leaving 1/2 inch headspace at the top of each jar. Add more liquid to cover, if necessary.
Wipe the rims of the jars. Place the lids and rings atop.
Once the hot water bath begins to boil, process for 10 minutes (half pint); see notes, below for adjustments in altitude.
Remove the jars and allow to cool on a folded towel. As they cool, you should hear the lids ping. Jars may take up to 24 hours to seal - once sealed, the center of the lid should not push up and down.
Store in a cool pantry for up to 12 months. Once opened, use jars within 7-10 days.