Apples work well if you dont have your piece. My bowl was chillin at a friends one time, so I grabbed a 2 litre bottle and all the other supplies needed to make a home made bong.

It sucked . So I grabbed an apple and did the following:
-Take stem out
-Using a thin knife, stab from the top where the stem was about 3/4 to the bottom. Don't go all the way through, don't twist and turn the knife. You only need a slit.
-Stab in the side of the apple for where you want to put your mouth. Twist the knife so it makes a hole. Make sure you penetrate the core of the apple.
-Scrape out all the goo in the hole you just made.
-Inhale through the hole to make sure you have a good ventilation.
-If so, put the weed on the top where the stem was.
-Light, and enjoy your Apple Bowl.