The covers for the bed cushions had started falling apart and some of the mattresses had an unpleasant smell so when Ikea had a sale of foam mattresses (34,99€ a piece) we bought 5 of them and cut out new ones, using the old ones as templates. We then ordered 15m of fabric from Germany and sewed new covers.

A bread knife was great at cutting the foam
Some moisture has reached the old mattress…
Here are some test pieces of different fabrics. The white one is for curtains
Tracing the template with masking tape
Little brother helping mom to sew his own bed
Ready and fresh!