Run bash command inside a running docker container

I need to run some bash commands inside my running Docker container. The 2 solutions are given below.

1) Run command from the actual terminal

sudo docker exec -i <container_id> echo "hello"

2) Run command inside pseudo terminal

docker exec -it <container_id> bash

Now we are inside our container with pseudo terminal. We can use bash command in this pseudo terminal.

echo "Hello"