Not exactly Coke Rewards, but it is rewarding and it is from Coke: https://cocacola.promo.eprize.com/bite18/
Log in for a chance to win a $25 Amazon.com Gift Card for you and a $25 Gift Card for a friend.
In case anyone is curious:
I have all 16 spots full in the March Madness Bracket Challenge. I entered again to see what would happen, and it said Sorry, you didn't win a team. Still got a sweepstakes entry though.
So the deal on this thing is you enter 25 codes into any Coke Rewards thing to get it. So you could knock out a lot of it with the March Madness game, or about half of it getting a free magazine subscription.
Here is the summary:
You can enter once a day. When you enter, you get two things. The first is an entry into the Sweepstakes, where they draw for a single winner of a trip to the Final Four in Minneapolis. The second is the "instant win". You get assigned a team in the Sweet Sixteen. If...
One per account, and I haven't tried using the same phone on a different account. I used all Diet Coke caps because I had a lot of them and did this before I saw your question.
Holiday Instant Win has opened. Prizes include an Amazon Fire Stick, an Xbox One, and gift cards.
https://us.coca-cola.com/holiday/
So far I have won a Large Coke at AMC Theaters, a $10 Nike eGift Card, and an Amazon $5 Gift card.