Pro tip: the next time you start getting a cold, get a pomelo or two, and continously snack on it while you sit at home being miserable.
It's a great way to get both water and easily-digested energy into your body, which is otherwise difficult because water tastes like shit and the digestive system tends to be put into standby mode while the body routes all power to defense systems.
In my experience it makes me feel at least 10% better. Combine it with pain meds and nose spray and a cold is almost bearable.