What was the charcoal liquid used for in the movie "We Own The Night"?

To absorb drugs?

Yes, it is used to counter the effects of weed, etc AFAIK

it’s used to induce vomiting, so you throw up any drugs you try to hide/swallow

The mixture was activated charcoal. This is created by heating charcoal over 600 degrees C. The process makes it very porous, meaning it has lots and lots of tiny holes. Due to this, it has a large surface area. The activated charcoal adsorbs (sticks) to chemicals, impurities, various things. The uses of activated charcoal include water filters (the ones you have in fridge/freezers and britta water filters). Its properties are also useful in people who are in danger of suffering from alcohol poisoning and/or a drug overdose. In this instance, they pour it into his nose and mouth, potentially preventing him overdosing on anything he has snorted or swallowed. If someone has swallowed drugs or alcohol, the carbon will stick to it, preventing it from passing into your system. This in turn, allows it to pass through your digestive tract without causing any harmful effects. In instances of alcohol or drug overdose, people would have a gastric lavage (having their stomach pumped) and following it, they would ingest activated charcoal. This would help in the way that stomach pumping can only clean out your digestive tract as far as your stomach, while the activated charcoal can pass through your intestines fairly rapidly and prevent any more drugs it encounters passing into the body.

Typically, activated charcoal would not induce vomiting, this would be done by an emetic, which induces vomiting. In the case in this film, he was not sick. The reason they give activated charcoal after pumping the stomach is that if the person was sick while being fed the charcoal, this would prevent the charcoal from working.

I did a case study on alcohol poisoning a couple of years ago on my Biomedical Science course, this is information verified from various sources and currently standard practice in British hospitals.

Currently, you can buy activated charcoal capsules over the counter to sober yourself up for work in the morning. I have never tried them. The theory is solid, however, I believe the adsorption properties are not rapid enough with low concentrations of alcohol to make them as effective as in someone with much higher concentrations, such as in a poisoning patient.