- For watermelon juice, purée 4–5 cups de-seeded watermelon in blender or food processor until liquid. Strain through fine-mesh strainer, pressing with back of spoon to help extract juice. Reserve.
- In small pot over medium heat, combine sugar and water. Cook until syrup comes to a boil, then add jalapeño. Let steep for 1 hour. Strain through fine-mesh strainer.
- In quart-size container, add 1½ cups watermelon juice, then fill to 1 quart with jalapeño syrup.
- Fill 12-ounce glass with finely shaved ice, then top with 8 ounces watermelon syrup. Serve immediately.
“I really like the watermelon-jalapeño because for me, personally, I need some kind of a punch in flavor. I couldn’t do watermelon by itself. Jalapeño gives it that kick at the end.”