Thinly slice onions and place them in a large glass jar. Now's the time to add in the peppercorns and bay leaf if you're using them. Set aside.
In a saucepan, combine water, vinegar, salt, and sugar. Heat on the stove, string occasionally until the sugar and salt are dissolved then remove from heat.
Cool liquid down a bit. Once it's warm, pour into your onion jar. Place the lid on top and refrigerate for a least an hour.
You're ready to snack! Enjoy!
Store in the fridge. They will last at least a month, but probably longer. Mine never seem to last that long. ;)