After drinking expired orange juice that is spoiled, you may experience nausea, vomiting, diarrhea and stomach upset, according to the Ohio State University NetWellness website.
Probably applies to old squeezed oranges too, since this is what I experienced today - the first three symptoms but not actually doing the latter two of these fortunately (empty stomach). Given that I was too lazy to throw them out and had run out of juice. I seemingly did pass out though - flashing images.
Well, won't be doing that again!