Yes, you can use stevia or Splenda as a substitute for sugar. However, it's important to note that these sweeteners may affect the texture and taste of the cake compared to using regular sugar. Stevia and Splenda are much sweeter than sugar, so you will need to use a smaller amount to achieve the same level of sweetness. You may also need to adjust the recipe by adding a small amount of additional liquid or another binder, as sugar provides structure and moisture to the cake batter. It's a good idea to experiment with different amounts of stevia or Splenda and adjust the recipe as necessary to achieve the desired texture and taste.