Heat oven to 350°F. Place the graham squares in single layer on baking sheet. One at a time, dip marshmallows in water; gently shake off excess water and roll marshmallows in sprinkles. Place a marshmallow onto half of your graham squares. (You should have an equal number of marshmallow topped graham squares and plain graham squares.) Bake 2 to 3 min. or until marshmallows are puffed. Immediately place 1 chocolate piece on each plain graham square. Sandwich chocolate and marshmallow-topped squares to make s'mores; press together gently to secure. Enjoy!