Most soups contain sodium especially canned soup so when you intake too much of that sodium in the soup then yes you can gain water weight from the soup.
That also goes for cured meats or any other salted foods when you eat them and then consume water along with the salty food.
Salt naturally follows water so when eating salty foods like soup especially canned soup then you can gain 2 to 3 extra pounds of water weight.
The water weight is usually temporary though and doesn't last long.