Bowser's Sourpuss Bread

From the Super Mario Wiki
Mario with Bowser's Sourpuss Bread
“You know what they say: All toasters toast toast!”
Mario, Hotel Mario

Bowser's Sourpuss Bread is a brand of bread that is used in Hotel Mario, in which it is being toasted by too many toasters in Roy's HardBrick Hotel, where it causes electrical flickering. As well as his name being on the product, the packaging includes a distinct Bowser logo, implying that Bowser's forces manufacture this bread.