Upgrading simple shells

Spawning TTY

If Python is present on the target machine, the first method below is very reliable. Otherwise, the other options are worth trying but don't always work.
python -c "import pty; pty.spawn('/bin/bash')"
Be sure to check for other versions of Python!
echo os.system('/bin/bash')
/bin/sh -i

Tab auto completion

The following commands will give tab autocompletion, but other features such as SIGINT, history, and clear screen will not work.
CTRL + Z (background the session)
stty raw -echo

Full TTY

The following commands will correct formatting errors and provide the remaining features including SIGINT, history, and the ability to clear your screen.
# on attack machine
stty -a (note number of rows and columns)
echo $TERM
#on target machine
export TERM=xterm-256color (match term from attack machine)
stty row XX columns XXX (match from attack machine)
echo $SHELL -- if not bash, export SHELL=bash