If you mean the actual Rewards Visa card.. something like this one
you sure can, it's a regular visa card
The Rewards card they send you with your points on it is the same thing, you can use it for anything, as long as you have enough points, I've had a purchase for $50.00 and only had 38 points, they swiped both cards, so i only payed $12 for the $50 dollar purchase