Wash all vegetables thoroughly. Cut cauliflower into florets, carrots into coins, cucumbers into 1/4-inch slices, red bell pepper into strips, and trim green beans.

In a saucepan, combine vinegar, water, salt, sugar, garlic, mustard seeds, and peppercorns. Bring to a boil while stirring until dissolved, about 3-5 minutes.

Place vegetables in a heat-proof bowl. Pour boiling brine over them, ensuring they are submerged. Let cool at room temperature for 1 hour.

Pack vegetables into sterilized jars, cover with the brine, and seal tightly.

Refrigerate jars for at least 24 hours before serving. For best flavor, wait 3-5 days.