Through OSHA (Occupational Safety and Health Administration). I.E. viewing unvaxxed employees as making the workplace unsafe. Businesses that don't comply will be fined.
Patriots should have fought hard against OSHA in the first place, because the whole concept violates the Constitution directly.
"A senior administration official estimated that this new OSHA requirement will cover about 80 million workers and businesses that do not comply with the agency’s rule can face substantial fees"
"So how does Biden have this power to mandate businesses require vaccination?"
He doesn't. Mandates are not laws. Executive orders only apply to executive branch offices. They do not apply to any other branch of government nor to any private business or person. They will lie lie lie to get what they want but this is all bull crap. He has no power to force us to do anything.