It looks like someone has spilled a lot of white wine, water or maybe gin! However it is just ... the 'Clumsy Coaster'.
You get a pack of 2 plastic coasters, which can be used as actual drinks coasters, in order to protect the table underneath. However they are also a nice illusion, since they look as if someone has spilled quite a lot of liquid!
When you have finished, you can simply lift the coaster off the table, and pop it back into the packet, ready for next time!
2 Clumsy Coasters, in presentation packet.