Combine vinegar, water, salt, honey, and garlic in a saucepan over medium heat
Whisk to combine well then heat until honey is fully dissolved
Remove from heat, set aside
Place sliced onion (and peppers if using) in a glass jar with a tight-fitting lid
Pour pickling liquid over the onions (and peppers) being sure to cover completely
Let sit one hour to marinate before using
Store in the refrigerator up to two weeks