Garlic, echinacea, elderberry, zinc and apple-cider vinegar work in synergy to treat a cold. Elderberry and echinacea have the most clinical data to support their efficiency if I remember correctly. Apple cider-vinegar clears sinus'.
Anecdotally, my recovery from colds at onset has been 1 day over past 2 years. This is assuming you take them immediately upon onset.
Not sure how long it would take 2 or 3 days in. Never got that far.