My experience. You feel bad. Anything ranging from ‘slightly off’ to ‘holy crap, this was a terrible idea’. Of course this directly correlates with the quality and quantity of the carbage you’re eating.
I don’t think it’s a terrible idea, I say go for it. Depends where you’re at in your progress though and what the likelihood of one beer turning into seven beers is. And then how much you think that’ll put you off your targets the following day/week/etc.
The one thing that surprised me is after being in ketosis long enough, the carb-ey food I used to love tasted bland. More importantly, the day after, I didn’t crave it anymore and I didn’t feel nearly as bad as I had eating junk food in the past.
Just my two cents, but I say, if you trust yourself, and you’re making a conscious choice about it, don’t worry about it. Have a day off every now and then. Don’t beat yourself up, recognize that you might feel terrible, and get back to the keep calm and keto on the next day.