It was a Nikko VaporizR2 RC toy. Dead one. So I removed all parts except motors, battery block and switch. The idea is to control it with Arduino from Android over Bluetooth.

Parts

Arduino Uno R3
Sparkfun Motor Driver (library and examples)
HC-05 Serial Bluetooth Module
PP3 9-volt Battery

Source code

In source code you can find:

an Android app to control the car
a Fritzing sketch to build hardware
an Arduino sketch

Car hardware

Android app

It is a simple app with two sliders to control left and right weels that sends commands to Arduino via Bluetooth serial.