How do you make cake batter thicker?
If you do want to thicken it up, just add more cake mix/dry ingredients and eggs/oil or whatever the recipe calls for in the appropriate proportion. I agree with comments about the consistency of your cake batter and leaving it runny if you are sure you followed the recipe and bake it as is.
What do you do if your cake batter is too runny?
How to Fix Too Much Water in a Cake MixScoop out some of the water with a spoon before stirring. This will help if you realize the mistake before mixing. Beat an additional egg into the batter. The egg will add viscosity to the mix and help it retain shape as it bakes.Stir in one box of dry pudding mix.