Julianne the carrots and slice the jalapeño

Place them in a glass jar (a 16 oz canning jar works best as it can handle the heat of the boiling liquid without breaking)

Bring the water, vinegar, sugar and salt to a boil.

Pour liquid over vegetables and allow to cool, then place lid on top and refrigerate.

You can use them within 30 minutes, but my preference is to eat them cold. I typically I make these the night before I make the Banh mi sandwiches (I also often make the peanut sauce the night before as well. It allows the flavors to come together)