What have you tried so far ?
Does it come from the front or the back of the car ?
Is the noise from both inside and out ?
Is there any sliding noise when you brake ?
Things to look at, jack / spare tyre in boot. Spanners or spare wheel nut under spare wheel.
Try emptying all compartments, parcel shelf, ash tray, coin holder, check battery restraint, seat catches, boot lock, wing mirror glass.