If/when you get sick, what do you do if your voice isn't in its "optimal place" (like it sounds gravel-y or coughing occurs when speaking in a higher register, etc.) but you landed voice-acting work that needs to be done?
There have legitimately been times when I just suck it up, try to get it as clear as possible, and record the work; if I need to hit a register with more bass, this is usually doable.
However, if the vocal quality difference is just super obvious (to me), I always make sure to reach out to the client and inform them of the situation, and offer to let them decide if it’s good to go anyway. “Hey, I am so sorry for any inconvenience, but right now I’m battling a small illness and I think it’s affecting the tone of my voice. Can you please check this sample for me and let me know if it still sounds OK, or if we should hold off on this for a day or two so I can recover?”
Only on a few occasions have clients said that it was passable (usually if quality wasn’t a major issue in the first place), but the overwhelming majority of the time they were more than happy to just give me a deadline extension, partially because I’d often work on this stuff before the deadline was even a concern. Part of my online/freelance marketing and branding includes providing super-fast turnarounds as often as possible (I can’t begin to count the number of times clients have replied to my submission with “Holy crap, that was fast”), and as a result when those periods of unavoidable illness do occur, there’s an extremely good chance my clients will be empathetic and happy to accommodate my needs.