Seafood soup usually tastes light and fresh, but if you want to add a touch of sweetness, consider adding the following ingredients:

1. Corn: the sweetness of corn can add sweetness to seafood soup, as well as add to the consistency of the soup.

2. purple potatoes: purple potatoes are a naturally sweet ingredient that can help temper the flavor of the soup and add sweetness.

3. carrots: carrots contain natural sugars that add texture and sweetness to the soup.

4. Onions: The sweetness of onions can add a light flavor to seafood soups.

5. dates: dates are a naturally sweet ingredient that can be added to the soup to add sweetness and nourishing properties.

It should be noted that the amount of these ingredients should be added according to their own tastes and preferences, to avoid adding too much sweetness, affecting the original flavor of the soup.