My pyjamas might seem to be a little much for other people (tank top, lightweight sweatpants, long cardigan & a scarf) but this is precisely the sort of situation that the outermost layers come in handy for, lol. Everything is in neutrals like browns, creams & khakis except for the scarves - they add a pop of colour to lift my face instantly (no makeup needed!) I go for a similar approach if going to work when sick but with a flat waistband (no drawstring trousers).
I'll sometimes add mirrored sunglasses if I look particularly bad but, out here (Hong Kong), it's common to wear a face mask as a courtesy to other people whenever you're sick (yes, even before the Coronavirus). So both sunglasses & a mask can make me look a lot more suspicious than I may want to be (like a celebrity trying to avoid the paparazzi), haha.