Soak a towel in warm water. Pick a towel large enough that it covers a large area of the rattan.
Place the damp cloth on the rattan and let sit overnight. Check the cloth, and if is still feels damp or moist, let it sit for several more hours. Both the rattan and the cloth should feel dry to the touch.
Remove the towel once it no longer feels moist. Let the furniture sit for at least 48 hours. The rattan absorbs the moisture, and once dry, its natural flexibility returns. Repeat the process for any other areas of the rattan.
Fill a spray bottle with warm water, if the cloth method failed. Spray the warm water all over the piece, giving the rattan an even coating of water.
Move the furniture to a dry location, and let it sit for 48 hours without using the piece. The rattan should absorb the extra water and become flexible again.