Heat vinegar, sugar, salt, and 3 cups water in a medium saucepan until simmering.
Put 2 garlic cloves, heaping 1/4 tsp. mustard seeds, and 1 tsp. pickling spice into each of 3 widemouthed pt. jars. Fill jars with tomatillos, pushing down to pack.
Pour hot brine over tomatillos to fill each jar to the top. Seal with lids. Chill to develop flavor, at least 4 days and up to 1 month.
Servings 0
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.