I was curious, so I looked up the equations. First: a handy graph of ISS altitude with time. The 400km altitude for ISS is only valid after an orbit raising burn. Just before each burn, the altitude can be 330km. An object needs to be in a circular orbit with an altitude of 160km to go round the Earth once. A tennis serve is sufficient to go from 400km circular to 400-160km elliptical. A fast bowler has enough delta-v to put a cricket ball into a 330-160km orbit from 330km circular. Just letting something float away so it misses the next orbit raising burn means it burn up in about a year.
Ignoring air resistance, a gentle throw antispinward will drop perigee by 50km and mean an object does one less orbit than the ISS in about a month. That should be plenty of time for air resistance to drop apogee well below the ISS.