This is a good question.
On the one hand any sentence that includes the word 'drink' can simply refer to consuming a liquid, but on the other hand we often use use 'drink' to refer to alcohol.
We probably wouldn't say "I want to drink" . It's more likely that we say "I want/need a drink" , and this can simply mean "I am thirsty" , but, as you said, it could mean "I want/need alcohol".
In certain phrases it's clearer. "You drink too much" probably means "You consume too much alcohol", but technically that's not 100% certain.
Therefore it really depends on the context