If you have any website and you want to promote that web site then this voucher can be used. Make a log in in Google Ad-words account and put there in billing option your coupon code after that make a campaign-> Ad Groups->Ads(Based on keywords). By following this process your account will be credited and your ad will be live on Google search engine in few hours. It's only one best use of your coupon.
If you use adwords voucher to run campaign, remember to stop your campaign when voucher balanced is used, otherwise, future clicks will be charged to your credit card, that can be really expensive if your campaign is not make money.