Whisk together pickling brine ingredients in a deep microwave-safe bowl. Microwave for 2 minutes, then whisk again to ensure salt & sugar are dissolved. Add the carrots. Make sure they are fully covered in the brine.
Microwave until the brine come to a quick boil (about 5-6 minutes). Microwave for another minute (you may need to stop it a couple times to avoid boil over). Remove from the microwave and set aside to cool.
When the brine has cooled to room temperature, drain. Refrigerate the carrots until ready to go on sandwiches.