If you missed it last time the deal is back. Add $25 to your Serve prepaid Amex card and you will receive $25. The last offer expired Sept 30th and this one is good till Dec 31st. I did it last time and got my $25 instantly after I added the $25 to my account. This is a one time deal, so if you’ve done this in the past you are not eligible.
Once you add the $25 and receive your bonus you can withdraw the balance to your bank account which is what I did. It’s $25 for minimal work, and there’s no reason not to do this.