It's not that they give them out for "about anything." You can take a look at the requirements here: https://en.wikipedia.org/wiki/Purple_Heart

In the example you described:

Type of injury: caused by shrapnel, so qualifies

Severity of injury: required medical treatment, so qualifies

Source of injury: This is the only real question. The description says that the injury may be caused by an enemy or friendly fire that was intended to harm an enemy. This definitely fails the requirement for friendly fire intended to harm an enemy, so we have to evaluate if the drunk soldier was considered an enemy.

I would say intuitively no, but who knows what they were thinking at that time.