How do you fake being really sick?

It is generally not advisable to intentionally deceive others about one's health by faking sickness. Honesty and communication are valuable in any relationship, including discussions about illnesses, aches, and pains. If health matters concern you, speaking with a doctor or seeking appropriate medical guidance would be a more productive approach. Focusing on well-being in an authentic way will be both personally beneficial and appreciated in your interactions with others.