Thinly slice the peppers and pack them into the jar.
Combine the vinegar, water, sugar and salt in a small saucepan. Bring to a boil, over medium heat, stirring until the sugar and salt dissolve.
Pour the warm vinegar over the peppers.
Let cool to room temperature then put a lid on them and store in the refrigerator.
Notes
These will keep in the refrigerator for 2-3 months. Salt - do not use table salt, it has unwanted additives. You can add fresh or dried herbs, fresh ginger (peeled and thinly sliced), and/or garlic cloves.