Hard one to answer because it really depends on the circumstances and the reason that you are having that drink. There is the champagne and orange juice breakfast celebrating the impending nuptials, the holidays that you have waited a decade for or a myriad of celebrations. Then there is the stark contrast of the person who has a severe addiction and their waking need is to have a drink. No judgement in either scenario just a statement that with every perspective there is a myriad of alternative views.
I think it depends on the social situation and the drink. If you are at the pub, then I think it is fine to have a beer in the afternoon, but for some reason, I can't help but feel that drink wine before 5pm is too early.
NEVER too early for a drink!!! I haven't had alcohol for breakfast before, BUT, if I went out for brunch, I think that would be okay for a glass of wine. If its a meal in a social situation or at a restaurant, that's ok.