canada
In Canada, there are the separate offences of:
- sexual assault (premised on lack of consent, no matter by what means consent is lacking; R. v. G.F., 2021 SCC 20) and
- administering a stupefying substance.
If someone were to use a "substance such as everyday alcohol" (I would reject the premise that this is "benign") for the purpose of facilitating sexual assault, this would be an offence under s. 246 of the Criminal Code. Section 246 makes it an offence for a person, "with intent to enable or assist himself or another person to commit an indictable offence" to administer or cause any person to take a "stupefying or overpowering drug, matter, or thing."
The Court of Appeal for Ontario has accepted that the element of administering a stupefying thing could be established by oversupply of alcohol. They have said that alcohol is a "stupefying substance" (R. v. Vant, 2015 ONCA 481) and can support a conviction under s. 246.
"Date rape" has no legal significance and even criminologically, misframes the circumstances in which people experience sexual assualt. Further, your premise that intimate partner sexual assault "usually happens when someone uses narcotics to drug another into an unconscious state" is not supported by the evidence. While this is a criminological point, rather than a legal point, it is important context for understanding such crimes. This 2005 study estimated that 4.6% of intimate partner sexual assaults were facilitated by surreptitious drug use. These two fact sheets describe the variety of circumstances, completely unrelated to incapacitation by drugs, in which people experience intimate partner sexual assault/violence: Fredericton Sexual Assault Crisis Centre Info Sheet; Centre for Research & Education on Violence Against Women & Children Backgrounder on Intimate Partner Sexual Violence.