I saw below on amazon GC page
Get a $5 reward when you reload your Amazon.com Gift Card Balance with $100 or more
Click on the "Reload Your Balance" button to go to the Reload page. Then, reload $100 or more, and receive your $5 Amazon.com Gift Card Balance. Your Gift Card Balance can be used to shop from millions of items on Amazon.com and there is no expiration date or service fee. Learn more from Amazon.com Gift Card Terms and Conditions.
We will send you an email to confirm your reload order, and the $5 reward. Enjoy shopping on Amazon.com.