Start by slicing the jalapeños. Slice these to your preferred thickness, try to think about the size per bite! This also depends on how big your jalapeños are. Pro tip - wear gloves when slicing so you don't get "hot hands".
Now make the brine! In a small pot over medium-low heat add in water, vinegar, sugar, and salt. Bring mixture to a simmer, and simmer for 5-6 minutes stirring occasionally. Everything should be fully dissolved.
While the brine is simmering, stuff the peppers into the mason jar. I use a 32oz wide mouth mason jar. Add in the whole cloves of garlic, and the peppercorns to the jar.
When the brine is done, remove from heat and pour brine over the jalapeños in the jar. Let this sit uncovered to cool for an hour. After an hour, add the lid and store in the fridge for up to 2 weeks. Enjoy!
