Can you use regular coffee for espresso?

Yes. But it will be watery, gross coffee. Use hot water to make the espresso, not filter roast coffee grounds. Blend 1 cup of hot water for every ½ - 1 teaspoon finely ground beans until you get your preferred strength. The key is that filtered grinds are too fine and baking powder or other additives don't dissolve properly in regular ground beans because regular coffee has a starchy residue on the surface which absorbs moisture during storage- regular coffee has very little aroma because the oils are trapped inside tiny soybean globules rather than being emulsified on the surface so there's no aroma escape- all this adds up to weak, thin espresso with bitter overtones... yummy!😂😂😂