"Some drug that blocks the euphoric effects of drinking" would be more accurate.

This is a significantly-incorrect, surface-level understanding of the "Sinclair Method". As another poster noted, naltrexone (or similar) prevent one from feeling much of anything from alcohol (though you'd still be physically impaired...). Without any dose (drink) --> response (pleasant-feeling) relationship, users tend to stop drinking significantly (because drinking doesn't really do anything)...

The "Sinclair Method" is, basically, to promise to take naltrexone (or similar) 30 minutes or so before you ever take a drink. That way, if/when you drink, you never feel the "drink" and your mind can return to normal.

No drug will "make you stop drinking" (though disulfiram may make you want to do so); the Sinclair Method attempts to remove your interest in drinking.

From what I understand, you take the drug before the act of drinking and it stops the habit-forming/positive-reinforcement chemical processes.