Slice cabbage into ribbons. Peel 2 carrots and using a mandoline or vegetable peeler, slice into thin ribbons, too. Clean and trim 2-3 ramps, then thinly slice. In a small pot, combine water with rice wine vinegar and ¼ cup sugar. Bring to a boil. Pour hot liquid over cabbage salad and let sit for at least 2 hours at room temperature; then cover and store in the fridge before using.
In a large saucepan, heat 1 1/2 inches of frying oil to 350 degrees over moderately high heat. In a medium bowl, whisk the flour with the cornstarch, baking powder and 2 teaspoons of sea salt. Whisk in the sparkling water until a smooth batter forms.
Working in batches, dip the broccoli in the batter, shaking off the excess, and fry until lightly browned and crisp-tender, about 4 minutes. Drain the fried broccoli on a wire rack or paper towels and season generously with sea salt. Serve immediately with the cabbage salad.