Sugar Soap is a salts based cleaner. Whilst it may remove some scale buildup it can leave residues on hard surfaces such as glass or stainless steel. There are more specialised products available in the Hillmark Range of cleaning products.
'Hillmark Scalex Plus':http://www.hillmark.com.au/Products/DescalersDegreasers.aspx is ideal for Washing Machines and Dishwashers.
You may also use the stronger Scalex product.