A grandfather is hanging out with his grandson

A grandfather is hanging out with his grandson.

He says to his grandson, “Hey Johnny, please fetch me the cup of medicine and the cup of soda over there.”

Grandson says, “Sure, gramps, but why the soda?”

Grandpa says, “I mix ’em together so that the medicine doesn’t taste so nasty.”

Johnny says, “Oh, good idea”, and starts to pour the cup of medicine into the cup of soda for him.

Grandpa says, “No, no, no. Another way around. You pour the cup of soda into the medicine, not the medicine into the soda.”

Johnny says, “Okay, but what difference does it make?”

Grandpa, a little irate, says, “What difference does it make??? Well, rather than ruining my wonderful soda with that nasty medicine, I’m making my nasty medicine taste better.”