L293D Motor driver 'braking' using input pins
That Wikipedia article is very poor. It doesn't even link to the datasheet or have a diagram of the pinout. Your question is similar to Braking a motor with power transistors.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Using the bridge to brake the motor.

I would expect that you should be able to give maximum braking by holding closed one of the already closed switches and let the freewheel diodes look after the rest. This will initially maintain the current and rapidly cause dynamic braking. If the current is running left to right through the motor then SW1 could be left closed or SW4. 

To simplify your control logic you can just close SW2 and SW4 each time you want to brake. The current through the switches and diodes just after braking is initiated will be the same current as immediately before braking and should decay as the motor decelerates.