Bing Rewards member in the US can claim 100 GB of free OneDrive storage for 2 years without spending any Bing credits. This offer is completely free. The only catch is that you have to agree to receive promotional emails from the company. But after getting your free 100 GB, you can unsubscribe the promotional emails, or even opted out of Bing Rewards.
The offer must be redeemed by Feb. 28.