You want a sponge? You could try a natural one but please do be sure it is sustainabley harvested… like these
Sustainable Sponge Farming
Sustainable Sponges are grown in the sheltered lagoons of Pohnpei, Micronesia. Sponge farming in Micronesia was started by the Marine and Environmental Research Institute of Pohnpei (MERIP) as a means of generating a sustainable livelihood for local community members, many of whom have no access to running water or electricity, and little means of earning money.
Read more and buy here.

If that doesn’t appeal you can buy biodegradable, cellulose sponges such as these.

ProDec Cellulose Large Size Sponge
Details:
100% cellulose for extra absorbency
Holds up to 20 times its own weight in water
150 x 115 x 40mm
100% natural cellulose sponge. Ideal for washing down and sugar soaping surfaces, hanging paper and cleaning tiles. Can also be used to help create special stippling effects. The super absorbent cellulose structure can hold up to 20 times its own weight in water, and when wrung out will wipe down surfaces leaving them virtually dry.
Buy them From ebay.

N.B.
You can get bath time versions that are more attractively shaped.
I have yet to find one in #plasticfree packaging

For washing up and wiping down I use these biodegradable cellulose sponge in compostable #plasticfree packaging. Fantastic. And I composted them in my bin when done. Read more here.