out like a light

(be/go) out like a light (fall asleep the moment one goes to bed, to faint or pass out from over-drinking or being hit hard enough to be rendered unconscious) — отключиться, вырубиться

Example 1: I was so exhausted that the moment I laid down I was out like a light.

Example 2: After just 2 beers she was out like a light.

Example 3: On the very first punch the boxer was out like a light. (Cheater's)