In the EU at least the denatured alcohols sold to the general public (e.g. as cleaning products) don't have enough actual poison in them to cause much damage.

The main thing they shove in there to stop you drinking it is denatonium benzoate ("bitrex"), which will make you _regret_ putting it in your mouth, but won't kill you because you'll immediately want to spit it out instead. The other ingredients are mostly to stop you trying to get the bitrex back out and then selling it as bootleg booze (thus evading the tax).