Well I get sick all the time so who knows 😆.

I have previously read that vitamin C is important for the body before you get sick, but not that helpful once you get sick. As in if you regularly have plenty of vitamin C you are less likely to get sick, but once you are sick no amount of vitamin C will make you get better quicker.

Edit: Turns out even the pre-cold effect is minimal:

Taking vitamin C every day to try to prevent colds won't protect most people from colds. It only slightly shortens the amount of time that they're ill. Starting to take vitamin C once you already have cold symptoms won't have any effect on your cold. https://www.ncbi.nlm.nih.gov/books/NBK279544/