I walked in on my brother and his wife having , embarred need some advise?

OK i went to go visit my brother today at his apartment and the door was open i thought he knew i was coming over i guess not i walked in on my brother and his wife having and ummmm it was very very very embarring and he and his wife just froze and looked at me and they both started cussing me out so i left but i want to apologize and get them something to make it up for my intrusion although i am pretty sure his wife did not tell him i was coming over because she hates me. any advise?