How to Make It
Combine vinegar, ½ cup water, sugar, salt, and garlic in a 16-ounce jar; cover with lid. Shake until sugar is dissolved. Add onion, cover with lid, and let stand for at least 20 minutes. Onion can be pickled and refrigerated up to 2 weeks in advance. Just before serving, drain onion and toss with cilantro and oil.