In a large pot of boiling, salted water, cook Brussels sprouts until tender, about 3 minutes. Drain Brussels and rinse under cold water to cool.
Pack into two (16-oz.) glass jars along with dill and garlic.
Return saucepan to medium heat and add in water, vinegar, peppercorns, mustard seeds, red pepper flakes, salt, and sugar. Bring to a boil and simmer until salt dissolves.
Carefully pour hot brine over Brussels sprouts. Let jars cool to room temperature.
Seal jar, refrigerate, and let sit for at least 3 hours before serving.
Recipe by 5* trending recipes with videos at https://food.theffeed.com/2020/01/16/brussels-sprout-pickles/