How to use $100 coupon code received 2nd time from Google

I have received 2 times Google promo code of $100 each. Once, I used one of them when I was new to Adword now, other is received for another Gmail id. These are only for new accounts.
As per Adword policy you can't open 2nd account. If you were me then How should you use these 2nd $100 coupon code... Have you ever done so.. if yes, then HOW?
Should I open a new account or let it expire.

 

maybe you can sell it at some forum for a price if you can't think of using it somehow!!!!