French toast does not discriminate. You can make it with supermarket sandwich bread or thick-cut slices from a fancy loaf. Even pound cake is fair game. If you can soak it in custard and fry it in a butter-slicked pan, you can French toast it.
And stale pandesal? Absolutely. Ryle's mom makes a rich and simple soak with eggs and three milks: fresh milk, evaporated milk, and condensed milk. Make sure to slice and open up your pandesal—exposing its soft interior will help it hold more custard.