On this states vary. In the Purton case I cited above, the California court held that the employer might be found liable because while the accident itself occurred off the premises of the employer and not while the employee was acting within the scope of employment, the employee nevertheless got intoxicated at an event hosted by the employer and the employer may be liable for the injuries caused in the accident. Specifically, the court stated:
As we explained above, a trier of fact could conclude that the proximate cause of the accident, Landri's intoxication, occurred within the scope of Landri's employment. Because a jury could find the proximate cause of the accident occurred at the party, before Landri even attempted to drive, the going and coming rule is not implicated and amounts to an “analytical distraction.” (Bussard, supra, 105 Cal.App.4th at p. 806, 129 Cal.Rptr.2d 675.) Stated differently, we focus on the act on which vicarious liability is based and not on when the act results in injury.
Purton v. Marriott Int'l, Inc., 218 Cal. App. 4th 499, 510, 159 Cal. Rptr. 3d 912, 920 (2013).
However, a number of other states, including the OP's state of Minnesota, take a contrary view. On facts very similar to the California Purton case — both cases involved an employee who was served alcohol at an employer sponsored Christmas party and then afterwards caused an accident while driving after the party — the Minnesota Supreme Court held the employer is not liable:
In the clear majority of cases raising the office party issue, the courts have refused to hold the employer responsible. E.g., Nichols v. McGraw, 152 So.2d 486 (Fla.App.1963); Brehm v. Dobson, 15 Ill.App.3d 285, 304 N.E.2d 149 (App.Ct.1973). Historically, courts have not allowed such a common-law action. See Employer Liability, supra. For example, in Halvorson v. Birchfield Boiler, Inc., the court refused to find a common-law action for civil damages against an employer who served alcohol at a Christmas party to an alcoholic employee who became intoxicated and injured a third party. 76 Wash.2d 759, 458 P.2d 897 (1969). See Edgar v. Kajet, 84 Misc.2d 100, 375 N.Y.S.2d 548 (N.Y.App.Term 1975). Section 317 has typically been used when the employee is acting negligently on the work premises, albeit during off-duty hours, such that the employer could control the employee's action. The difficulty in discerning when the employer's duty to control ends, leads us to reject extending that duty to off-premises actions. Since Cortright was neither on the premises nor using the employer's chattels, we reject the applicability of the Restatement to this case....
Therefore, we reverse the court of appeals' holding that an employer as a social host is liable for negligently serving alcohol to its employee when the employee injures a third party off the premises of the workplace.
Meany v. Newell, 367 N.W.2d 472, 475–76 (Minn. 1985).
So we have two cases with very similar facts but two distinctly different outcomes. This is one of those situations in which state law really does matter. Unfortunately in Minnesota the case law does not support holding the employee liable for an intoxicated employee's accident on the drive home even when the employer itself served the booze to the employee. Given that, an employer isn't going to be liable for that accident when the employee is drinking his own booze during work, either. The result in other states, like California, may be different.