Is it okay to take multivitamins at night?

Yes: however, I suggest not taking them on an empty stomach.

Yes: Multivitamins are just as effective at night and during the day: a waste of money. Unless you are on a very strict diet, pregnant or fighting a chronic disease, multivitamins are pretty safe and worthless. If you have a specific lab proven deficiency, then take that one. Otherwise, save your money and buy a gym membership. Exercise has proven health benefits. Multivitamins, not so much.