as you say "CURRENT SINKING..!!"
means sinking of current or simply providing a path to the current from the load to ground...
so the the logic level of the ic must be low or GND
I know one condition. If a load is not grounded and it is connected to VCC, the TTL will draw current from it. An application of such configuration would be the connection of a load to an open collector TTL package.
A load of a TTL can be a resistor, a capacitor, or a current source. You will refer to a electrical characteristics part of a TTL Datasheet. They specify the test conditions and limits of a TTL.