Add the sliced poblano peppers to a 1-pint mason jar or other sealable heat-safe container.
Add the champagne vinegar, water, sugar, salt, and garlic cloves to a small saucepan.
Heat over medium heat until the sugar and salt have dissolved.
Using a funnel, pour the brine mixture over the peppers into the jar to cover.
Cover and refrigerate until ready to use.
