I am looking for a word that can be used to describe alcoholic beverages, coffee and tobacco products collectively. The closest I can think of is "drug," but that is too broad. Namely, it includes other substances that are not nearly as widely socially and legally accepted, as well as some forms of medicine.
I think I may have it, it's a bit of a cheat but it would comprehend substances such as caffeine, nicotine, and ethanol. It is normally written as two words, legal stimulants, but by adding a hyphen you can make it into a compound word.
Stimulants (also often referred to as psychostimulants or colloquially as uppers) is an overarching term that covers many drugs including those that increase activity of the central nervous system and the body, drugs that are pleasurable and invigorating, or drugs that have sympathomimetic effects.
@James McLeod correctly pointed out, in the comments below, that alcohol is classified as a depressant. Despite its name, a depressant does not make a person feel depressed, it is a substance which slows a person's physical and psychological responses. Therefore, if the OP is writing for a medical or an academic journal, the expression "legal-stimulant" would be completely erroneous.
On the one hand, the consumption of alcohol and cigarettes is often called a vice but on the other hand, it would exclude coffee and tea despite both containing the stimulant caffeine.
Addictive-substances might be a possible solution, seeing as all four drugs are addictive but just like the term “drug” itself, an addictive substance would also include narcotics: tranquilizers, sedatives, stupefacients, etc.
Legal recreational drugs
I assume that it is acceptable to use a term which includes tea, as well as coffee. Trying to find a term which includes one popular caffeinated hot drink and not another one will be completely impossible.
Alcohol, tobacco and caffeine are legal in most places. Alcohol is illegal in some Muslim countries, but they generally don't use English as their main language.
What sets them apart from other legal drugs is that they are used recreationally. This means the term doesn't include things like painkillers.
Some places will have other legal recreational drugs which are harder than alcohol, tobacco and caffeine. In the UK, all recreational drugs are illegal except a few whitelisted drugs (notably alcohol, tobacco and caffeine), so the term is very accurate in the UK.
Elsewhere, you could use the word "soft", i.e. "legal soft drugs" to indicate that hard drugs like Mephedrone (probably illegal most places now, just an example) are not included. Describing drugs as hard or soft is generally only done with recreational drugs, so using it with "recreational" would be redundant.
If you are concentrating on the effects on the nervous system, psychoactive substances are substances which act on the nervous system in a stimulating or depressing way. As an example of usage, this is the legal definition in the UK:
Notice that the legal definition in those pages explicitly excludes alcohol, coffee and tobacco, but you can infer the wider meaning from the text.