If you are in a desperate pinch, get like 2 table spoons of epsom salts (plain, not the bath salts), dissolve in water and chug, it tastes like ass but draws water from your body to your colon. Drink as much water as you can until you poop. The magnesium binds to your poop and draws water to itself so the more you drink the softer your shit becomes and the added water weight stimulates your muscles and helps get things moving