If you're asking why medicine tastes bad, I would guess that it's part of your defense mechanism. Your body evolved to reject things that could be dangerous. Sugars, like in fruit, taste good, while spoiled food tastes bad. Medicines are usually large, complex molecules or collections of molecules. These large molecules have a lot of complexity, which means there is a lot of potential to be picked up by your taste buds. Since these molecules are usually very different from what your body knows, you find the taste bad or strange. And the natural defense mechanism is to want to spit it out. I'm not a biologist and I haven't read anything on this. It's totally a guess on my part, so it's probably wrong. But you shouldn't be getting medical advice from a cartoon forum anyway.
Can someone explain why the sky is blue?