One soup can become several different soups with a simple adjustment of the recipe. A sweet French onion soup, for example, can become more savoury if you adjust the recipe to counter the sweetness of the caramelised onions. With some simple adjustments, you can fix too-sweet soups cooked from scratch as well as soups you buy premade.
Use smaller amounts of the sweet ingredients in the recipe when preparing a soup from scratch. Add only 1/4 cup of sugar to start, for example, if the recipe calls for 1/2 cup. Taste the soup after each addition to determine when you achieve the desired sweetness.
Add more salty ingredients to the soup to counteract the sweetness. Add more salt to a chicken noodle soup, for example, if you find the sweetness of the carrots overbearing. Add a little of the salty ingredient at a time, tasting after each addition to determine the difference.
Add more sour ingredients to the soup to balance the sweet flavour, since soups typically consist of a mix of flavours. Add lemon juice to a tomato soup recipe or more vinegar to sweet-and-sour soup, for example. Add a little of the sour ingredient at a time and taste after each addition to check the flavour.
Add more spices and herbs to the soup after you reduce the sweetness to liven the flavour.
Don't overcook sweet vegetables such as onions, carrots and peas. Doing so makes these vegetables taste overly sweet in soup.