Amend according to your preferences, run it whenever something annoys you, throw it in a cron job, etc.

.bash_aliases:

alias blocksocials='(echo ""; echo "127.0.0.1 reddit.com"; echo "127.0.0.1 www.reddit.com") | sudo tee -a /etc/hosts > /dev/null'

alias unblocksocials='sudo sed -i "/reddit.com/d" /etc/hosts'