"You do not want alcohol."
Translation:तुझे शराब नहीं चाहिए।
Nahin is one accepted way to transliterate नहीं without using diacritics. Nahi is wrong because it doesn't indicate nasalization. The most accurate way would be "nahīṁ" but unless you have your keyboard set to Linguistic Nerd Mode like me it's a pain to type. Nahin is much more common.
It's almost always left out if 1) you're negating the main verb (नहीं is present) and होना is not the main verb. मैं जाता हूँ / मैं नहीं जाता -- here you can leave out होना because it's not the main verb. However, suppose I want to negate मैं लड़का हूँ. I can't drop होना because it's the primary verb, so I must keep it in: मैं लड़का नहीं हूँ.