So I made this today:

Looks scrumptious and divine, right? It was. Calorie-laden and diet-breaking? Not even close.
It's a Diet Coke cake. That's right, it's made with Diet Coke. I was skeptical, too, at first, but I decided to try it to satisfy the curiosity of my co-workers and all of you out there.
It's very simple. Buy a chocolate cake mix. Instead of adding eggs, milk, water, whatever it requires, you add a can (12 ounces) of Diet Coke. That's it. Then bake as directed.
To ice it, I mixed one 12-ounce tub of Cool Whip Free with a package of instant fat-free chocolate pudding. Once the cake was cooled, I spread it on thick with a spatula. If it's going to be around for a while, you'll need to refrigerate it. I brought most of it to work, so I didn't have that problem.
My husband and I, who both hate the taste of Diet Coke, couldn't detect it in the finished product.
Messages throughout the night from my skeptical co-workers:
"dude, it's amaaaaaaazing!!!"
"oh my! delicious! im totally making that at home. ... it tastes like real cake. i can't taste diet coke at all."
"man, there's cake left. i'm going in. again."
Chocolate cake mix (not prepared)
Calories per serving: 160
Calories from fat: 25
Fat: 2.5 g
Diet Coke
Calories: 0
Fat: 0
Cool Whip Free
Calories per serving: 15
Fat: 0 g
Jell-O fat-free chocolate pudding mix (not prepared)
Calories: Less than 6 (It's 35 at 4 servings, so at 24 servings, I'm figuring less than 6 calories a person. Let me know if my math is off.)
Fat: 0 g
Total per serving:
Calories: 180-181
Fat: 2.5 g
WW points: 3
Making a regular cake mix (before icing):
Calories: 260
Fat: 2.5
According to some message boards I read, you can also make this with any sort of diet soda. Make a black forest cake with diet Cheerwine. Make a lemon cake with diet Sprite. Or try any of the many diet sodas that are out there, combined with some fat-free Cool Whip and fat-free pudding mix. Let me know if you come up with any great combinations!