Well, almost anywhere. There are places where if you have a beer with lunch and they saw you arrive in a car, they'll ask you for your car keys otherwise they'll call the police on you. Daily life works differently around the world :)
In Singapore you wouldn't necessarily arrive in a car (yet alone your own car) when you go to a car showroom. I'm not even sure they'd have enough parking around there.
See https://earth.google.com/web/search/BYD+Zhongshan+Park+1826/... for the location.
And many people bring a companion when they do a test drive. Filling up the companion is perfectly legal and fine.
For those without religious objections or addictions, one glass of beer or wine with a meal is a complete nothingburger. Yes, it technically impairs your reaction times, but not enough to be a crime.
Though I suspect the BYD folks would want to avoid any hint of impropriety, so they probably will only let you drink there _after_ your test drive.
But I've only ever ate and drank at their showroom, I never went to the car side of the business.