Prepare asparagus by cutting off the ends. Place the asparagus and sliced garlic cloves inside a jar tall enough to fit them.
In a medium pot, combine the water, vinegar, sugar, salt, and peppercorns. Bring the brine to a boil.
Pour the marinade over the asparagus. Let it sit for 15 minutes, then seal with a lid. Allow the asparagus to marinate in the fridge for at least 24 hours.