This whole "donate points for a chance to get a bunch" thing seems to be catching on, although February's Heart Truth promo is on the confusing side. That link can be found through the bonus offers page, which reads, "Dbl. Pts. on Diet Coke® w/ Donation Enter The Heart Truth™ multipack code AND donate pts. to it in Feb. Credited on 3/8."
If the promo is similar to last year's, there are special 12-packs to promote the event. This program isn't as good as the current Arctic Home game, since each double-points code will only get you an additional 10 points but, if you drink a lot of Diet Coke, there is an opportunity here (It costs 35 points to enter.). Keep an eye out.
Special thanks to Team Flyertalk for pointing it out.