It is real, the sweepstakes sponsor is Microsoft, and the bitcoin card is one of several giveaway prizes that you can independently enter.
https://www.bing.com/rewards/redeem/000300000246 - However, you cannot enter without making a Bing Rewards account; even the "no purchase necessary" clause demands that you complete Microsoft's goal, which is to get you (and your info) into Bing:
ALTERNATE METHOD OF ENTRY: To enter without purchase and without redeeming any Bing Rewards credits, visit
http://www.bing.com/explore/rewards and follow the links and instructions to
create an Account (if you do not already have an Account). Then, on a 3" x 5" card or piece of paper, hand-print your full name, complete address, phone number (with area code), date of birth, email address, and the number of the sweepstakes which you wish to be entered into, and mail it to ""Bing Rewards August 2015 Sweepstakes", Free To Enter", P.O. Box 8554, Big Sandy, TX 75755-8554. you will receive one (1) entry into the applicable sweepstakes.
Requests must be postmarked by August 31, 2015 and received by September 8, 2015. Only one (1) entry per envelope allowed. Entries mechanically reproduced or made in any fashion other than as specified herein are void.
Entries submitted by script, macro or other automated or mechanical means, entries by any means which subvert the entry process and entries made in any fashion other than as specified herein are void. All entries become property of the Sponsor and will not be returned.