When passing an object into a function, should the function bother returning a value or just update the object by reference?

sample.cs

            // Populates with some data from the API.
            ProductInfo productInfo = parseApiReply(apiResponse);
            
            // Need to update some empty fields after doing some logic on the data from the API.
            
            // I've been following the general guideline of always return a value so I write this:
            productInfo = addUserInfo(productInfo, userID);
            
            // But is it pointless to set visitorSerialInfo there since we can update it by reference in?
            // I could just do this:
            addUserInfo(productInfo, userID);
            
            // Which is best in this case, and why?
            
            // Of course, I could create two more objects and combine them,
            // but that seems like overkill. addUserInfo will just be 6 lines
            // or so and will update only 3 fields.