How do i make a tolerable bad tasting cupcake?

i have a school project about the poem "siren song" and have as an attention getter to our project we are making cupcakes. 1/2 of the batch will be normal cupcakes and the other 1/2 will be bad tasting. we are going to decorate the bad tasting ones so they look very appealing and the normal ones really badly. how do i make cupcakes that taste bad but not bad enough where my whole class would be mad? like what is an ingredient i could change