Pour both dry cake mixes into a gallon-size Ziploc bag.
Zip it up tight and begin to shake it well to make sure cake mixes are combined thoroughly.
In a clean mug (you do not need to grease the mug), combine 3 tbsp. of the combined cake mixes with 2 tbsp. of water.
Stir well until completely combined. Batter will get foamy as you stir.
Then pop it into the microwave.
Cook on high for 1 minute.