One of my husband's co-workers brought this to work. It is nothing fancy, but if you need a very basic cake, this is the ticket.
1 box cake mix (any flavor)
1 can diet soda (any flavor)
Mix together. DO NOT ADD EGGS, OIL, ETC. Just mix cake mix and diet soda. Pour into 9x13 pan that has been sprayed with cooking spray. Bake at 350-degrees as directed on cake mix package--probably around 30-35 minutes.
That's it! It is best to use colas with chocolate cake mix and lemon-lime type sodas with lighter cake mixes. I had a box of red-velvet cake mix that we mixed with Diet Coke. It was pretty good! This is a great idea for college students in a dorm who may have access to a common kitchen but don't want to buy eggs, oil, etc for the usual cake mix. Top it with a scoop of ice cream or a dollop of whip cream and it will look pretty special. Let me know if you try it!