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

"I want a drink" "I want something to drink". "I need to drink something" --> is probably a little better when you have to emphasis the seriousness of your thirst.

First choice: "I'm thirsty". However, "I want something thing to drink" is fine and does not give the impression you are looking for alcohol, unless you are in a bar. (Context matters.)

*person