This is a complicated question. There are many
types of fabrics, and they are made from a variety
of natural materials (like animal coats, cocoons
of silkworms, plant seeds, leaves, stems, etc),
synthetic (or human-made) fibers (made of
plastics, chemicals, or natural materials), and
combinations of the two.
When you pour water on a fabric, it will
not hurt it, but it may cause changes to the
fabric properties. For example, when silk gets
wet, it will shrink as it dries. When you pour
water on a fabric like cotton, the water molecules
get inside the cotton fibers and inflate them
(like when you add water to a dry sponge and it
plumps up). For cotton, those water molecules will
actually attach to the cotton fibers and make the
fabric more resistant to breaking.
Other fabrics respond differently. And
sometimes the fabric is treated with water
resistant chemical coating so water will bead up
and roll off the fabric (like when you pour water
on a plate), but even that fabric will eventually
become soaked if enough water is poured on it (or
the fabric is put into a bucket of water).
All that said, traditional fabrics will not
grow when water is added to it. However, there
are new technologies in microbiology using
microbes to create fabric-like materials by
feeding them sugar and drying out the resulting
substance. It is possible that adding sugar water
to such a fabric, if the microbes were still
present, could grow fabric.
By 'fabric,' do you mean cloth? You can
pour water on cloth. Most cloth gets washed in
the washing machine, with soap and water. Some
cloth needs to be dry-cleaned, without water.
Cloth doesn't grow when you pour water onto it.