Place the banana peppers, jalapeno peppers, and serrano peppers into a large pot. Add the vinegar, water, garlic, and onion. Bring to a boil, then reduce heat to medium-low, and simmer for 5 minutes.
Ladle peppers into sterile jars, and fill to the top with the liquid, leaving 1/4 inch headspace. Tap jars on the counter to remove air bubbles. Place two piece lids on the jars.
Place jars in the rack of a large, canning pan, and fill with enough water to cover the jars completely. Bring to a boil, and boil for 10 to 15 minutes. Refrigerate jars after opening.
