Theraflu is honestly my go-to thing for whenever I'm feeling under the weather. It clears up my symptoms and ends whatever's messing with me much more quickly than it would end by itself.

The only problem is that the drink tastes just horrible, so if you go with that option, as opposed to the other forms, I'd suggest to mix it up as a shot. You boil up some water, mix it until it won't mix anymore in a shot-glass (kool-aid sugar style!), then down it. Makes it much easier than using a whole coffee mug. Then chase with something like orange juice.