DISCLAIMER: this is not medical advice.

I used to get sick a LOT as a kid, and that has not really changed well into my 30s. The difference was to start mega-dosing on vitamin C at the first sign of cold symptoms and to keep at it until fully healthy. Specifically, at least 3 times a day I take 4 or so pills of this: https://www.walmart.com/ip/Spring-Valley-Vitamin-C-Supplement-with-Rose-Hips-500-mg-250-count/893225

Since kids don’t like swallowing pills, I have them take this instead in similar (but somewhat lower) dosage: https://www.walmart.com/ip/Spring-Valley-Vitamin-C-Chewable-Tablets-Dietary-Supplement-Tropical-Fruit-Flavors-500-mg-200-Count/10324589

Emergency C seems to work well too, but it is both pricey and more cumbersome due to requiring a water bottle.

A more cost-efficient (and potentially healthier) alternative to Emergency C is 1 gram of vitamin C powder mixed with erythritol (for taste, better option than regular sugar) and/or gatorade powder (for taste and to prevent dehydration but with the drawback of adding more sugar to your diet). Yet, it is even more inconvenient than Emergency C.

If you are already sick, a mix of Mucinex DM and pseudoephedrine (but not phenylephrine) should give some comfort, and if you need some energy to deal with mental fog, add small doses of caffeine.