In a cronjob, I want to execute a date sub-command and substitute the results in place into the overall shell command. Something like:

1 5 * * * bash -c 'cp /foo/bar /foo/bar.$(date +%Y%m%d).sql'

Unfortunately, this breaks with an error at runtime:
/bin/bash: -c: line 0: unexpected EOF while looking for matching `'' /bin/bash: -c: line 1: syntax error: unexpected end of file

I am obviously missing something here.