  One answer might be that one can’t. Another might be that one can, and by asserting “You (do) want to get drunk every evening”, but  only by deriving the consequent “You should work in a bar” in a heavily qualified and contextualized sense: working in a bar may fit getting drunk every evening as a necessary means; hence one might say “You should work in bar”, but only if it is implicit that the fittingness that “should” connotes exists only in relation to the goal in question. (So, of course, no recommendation of working in a bar follows.) Hare, however, permits himself a bold solution. He takes the clause “you want to get drunk every evening” to be have different meanings in (a) and (b). In (b), it is an embedded indicative, ascribing a desire to you—which is why the consequent can be detached by asserting “You want to get drunk every evening”. In (a), it is an embedded imperative, which would serve on its own for advising you to get drunk every evening; therefore the consequent can be detached, but only by prescribing “Get drunk every evening”.