The best pillow will keep your head and neck aligned while you are lying down. ✔️ Fill: Any fill from down to foam can work for side sleepers as long as the pillow is thick enough to support your neck. ✔️ Loft: This refers to the pillow's height. If you stay put on your side all night, a solid memory foam pillow can support your head in one position to help keep you asleep. In our evaluations, some pillows could not be washed at all, while even more pillows only have machine-washable covers.