作为额外添加用英文怎么说

"As an add-on" or "as an additional" are common ways to describe something that is being added or included in addition to something else.

For example:

"I'm offering a discount on my services as an add-on for anyone who books a package deal." (我为预订套餐的人提供服务折扣作为额外添加。)
"As an additional service, we offer free depvery for orders over $50." (作为额外服务，我们为超过50美元的订单提供免费送货。)

These phrases are used to describe something that is being added or included in addition to something else that has already been mentioned or is already being offered. They are commonly used in business and marketing to describe extra features or services that are being offered to customers.