Methanol is only a health risk when distilling.
Its probably acetaldehyde. It's a natural byproduct of fermentation. With an uncontrolled fermentation and bread yeast, you probably produced a lot of it.
My above equation should really read:
Water + sugar + yeast => water + alcohol + carbon dioxide + X
X is all the byproducts of fermentation. X is comprised of: esters, phenols, aldehydes, fusel alcohols (longer chain alcohols than methanol & ethanol), acids, and more.
If you want it to taste good and not give you headaches, then you need to control X. That's the difference between hooch and wine.