Some suggestions: Pick up a rock and pop it into your mouth. Suck on it as if it were a piece of hard candy.
Spend a hour on your back on a hardwood floor
Lay your head on a stranger's lap.
Eat a banana veeerrryyy slowly.
Whistle the same note while cooking dinner (my grandma millie used to do this)
Sit on the edge of a table. Convince yourself if you were to jump off of the table you would fall into a deep canyon and perish.
Dress up as a baby and visit a nursing home.