kali debian apt sources code example

Example 1: source.list kali linux

Try this:
sudo apt-get update --fix-missing

Example 2: kali repo

echo "deb http://http.kali.org/kali kali-rolling main non-free contrib" | sudo tee /etc/apt/sources.list
echo "deb http://http.kali.org/kali kali-last-snapshot main non-free contrib" | sudo tee /etc/apt/sources.list
echo "deb http://http.kali.org/kali kali-experimental main non-free contrib" | sudo tee -a /etc/apt/sources.list