I've found this recipe in various places on the internet. I like it better than the traditional cake in a mug recipes that use egg because in my opinion they turn out too "eggy."
1 box angel food cake mix
1 box cake mix of your choice
Mix both dry cake mixes together in a gallon sized ziploc bag.
Put 1/3 c of the mix in a microwave safe mug. Mix in 3 Tbsp water. (Or you may use 1/4 c mix and 2 Tbsp water.)
Microwave on high for 1 min or til cake is done. Dump on plate or eat straight out of mug. Frost if desired. Makes 1 serving.