My experience of using petrol injector cleaner is to use it in a quarter of a tank or less, not a full tank. The injectors are not going to notice it in a full tanks worth of fuel.

Used like that, it can work, put in in the tank, drive it a few miles, let it stand etc.

We don't know if your car is petrol or diesel?

If you have petrol injectors these people clean them properly.

www.injectortune.co.uk/index.html

Petrol fuel injectors rarely go faulty, but the nozzles do become partially blocked with varnish, gum and carbon deposits over time. This affects the spray which leads to inefficient combustion. The fuel pressure at the injectors on your car is only about 40psi, compared to around 30,000psi on a typical common rail diesel. As the above poster says, the best way is to have them properly cleaned on an ultrasonic machine. They'll then be as good as new.