If you travel frequently on budget airlines, you will definitely bemoan the restriction placed on carrying liquid-water on board as this means that you will have to buy your drinking water from the airline at an inflated price. Well, I found out that the restrictions on bringing water on board is only partially being enforced in most airports.
If one travels on AirAsia from their KLIA-LCC terminal, one will be checked at the security and so no water will be allowed through. But water can be purchased from the book shop within the security area and in theory the bottles must be put in a specific sealed bag (not just any sealed bag) which can be purchased from the same shop at a couple of Ringgit extra. However there are actually no more security checks as one board the plane- so it is redundant to pay and use the seal bag- just buy your bottled drinks and carry with you.
The same goes for most airports in China, such as Guangzhou and Macao. Just make sure you do not carry any water with you when you pass the security and then buy your bottled drinks from within the security zone.