you are Hungry.

or you maybe experiencing synethsesia, which is basically the mixing up of senses; anything from seeing sounds to hearing colors. This can happen naturally or can result as a side effect of some psychadellic drugs. For instance, in one study a person, ever since they were young, would always taste different things when they heard certain sounds, like tasting eggs whenever hearing a "K" sound. Either that or your friend is just a nut job hope this helped