this is why you should give yourself enough time, because writers block gets worse when you leave it at the last minutes.
Since it's due tomorrow, just start writing. It doesnt matter where you start, just do it (actually, this works even if it were due in 3 weeks). First, write a very brief outline. Just know what it is that you want to say and argue. Then, try working on the intro. If you still cant get anything out, move on to the body paragraphs. When you are done, base your introduction on the body paragraphs.
Remember that your intro needs to basically outline what you will say in the rest of your essay. You should say exactly what you will write later, leave that for the body paragraphs, but at least mention some of the points that you will later make. Maybe your very first sentence should be a statement.
Something like (here's a crap statement, its not even true. Im just giving you an idea): The consumption of alcohol has become such an integral part of our culture, often consumed during social gatherings and even as a way to "de-stress", that many businesses thrive on their selling of this substance (this sentence stinks). Although alcohol is very common in today's society, underage drinking has become a problem that affects both, drinkers and non drinkers.
That "sample" introduction was garbage, but i just wanted to give you an idea of how to introduce the topic.
I'm a procrastinator so I was in this situation a lot. And I'm terrible at writing introductions.