Divide pickling spice among 2 8-ounce jars or 1 16-ounce jar.
Cut cauliflower into small florets, discarding any leaves or large stem pieces. Pack into the prepared jar(s).
In a small saucepan, combine vinegar, water, pickling salt, and sugar. Bring to a boil, whisking to dissolve sugar and salt.
Pour over cauliflower, filling the jar with ¼-inch headroom. The cauliflower should be completely covered, but you might not use all the brine. Use a chopstick or wooden dowel to remove any air bubbles, then add more cauliflower or brine as needed.
Screw on lid(s) and let cool to room temperature before transferring to the refrigerator.
Notes
For pantry storage, process jars in a water bath canner for 10 minutes.
Let pickle for at least 48 hours before eating for best flavor.