Well, one should think outside of box, I mean United.

If one has AMEX Platinum, then there is Centurion lounge at the end of T3 going towards Terminal G

If once has Priority Pass (non-AMEX) - there are several restaurnts: one at Terminal G and two at T3.

But the best option (if coming from home) is eat at home or stop by at Panera Bread one exit before SFO.