In a medium saucepan over medium heat and add apple cider vinegar, water, dark brown sugar, and peppercorns.

Cook until the sugar dissolves.

Reduce the heat to medium-low and add in cherries and thyme.

Cook for about 5 minutes until the cherries have just started to soften.

Add cherries to the quart jar and top with strained vinegar mixture.

Let cool on the counter, cover, and refrigerate. Let sit overnight before using it.