Scotch, I think. Probably self-medicating.
Not kidding...I'm pretty sure he was a bit touched in the head. Frankly, he'd have to be, to rally Britain after the fall of France. He'd also have to be to proliferate the excessive multitude of special forces (e.g. Popski's Private Army, SAS, SBS, LRDG, Commandos, Para, SIG, etc.) as he did.
Churchill was more or less a high-functioning lunatic, for better and worse.