Unfortunately this is a really common issue in apartment buildings. A part of the problem is that (from my understanding) the BCA only says that “habitable” areas need to be waterproof and a car parking space is not considered a habitable space. Unless the construction plans originally called for a waterproof membrane to be installed it may not be considered a building defect.
The installation of evaporation trays is a very common “solution” also as the likely cost of waterproofing the top side of the concrete slab is often seen as prohibitive.
Evaporation trays will work only if the volume of water being caught by them is small so it has a chance to dissipate before the tray overflows. Ideally there should be by some sort of overflow or drainage pipe directing the water away from the car space.
It may not be an ultimate solution but it should be quick and relatively easy one to carry out.