"Added on" is a commonly used phrase that means an inclusion of something extra to an already existing item or situation. To express the same meaning, one can use various synonyms such as "appended", "supplemented", "enhanced" and "augmented". Other possible synonyms could be "inserted", "accompanied by", "attached to", "included with" or "fitted with". These phrases give an explicit implication of addition to something that already existed. One may use these words as alternatives to "added on" to impart variation and precision in their writing or conversation. The use of diverse vocabulary demonstrates a good command of language, making one's communication more effective and engaging.