Take 2 wide-mouth pint jars with lids and thoroughly wash them with warm soapy water. Rinse them well. Set them aside to dry completely.
Clean and dry off cucumbers. Slice them the long way into evenly cut spears. Halve and thinly slice the onions.
Evenly pack the jars with cucumbers, dill sprigs, and onions, leaving about a ½ inch space at the top of the jars. (Be sure to pack them as tightly as you can!)
In a small saucepan over high heat, bring the following to a boil: both kinds of vinegar, water, sugar, garlic, salt, and all other seasonings. Reduce heat and allow the brine to simmer until salt and sugar dissolve.
Cool brine down to warm and fill jars, still keeping the ½ inch space at the top of the jars.
Place the lids on the top of the jars and screw them on so they are sealed very tightly. Allow jars to cool down to room temperature.
Place the jars in the refrigerator for 24 hours. They will improve with flavor over time but will be ready to eat within a day!
Notes
Make sure to slice your cucumbers in a way they will fit into the jars easily.