You can tie-dye lots of things like t-shirts, pillow cases, handkerchiefs.  The easiest and cheapest thing to dye is socks

Follow the instructions on the packet or tin of dye that you have bought. Read this carefully before you do this activity because some dyes need salt and some cold fix. And make sure that you have enough time to do this - some dyes require things to be soaked for 3 hours, some for only 1/2 an hour.

You will need a pair of white cotton socks for everyone.

Twist each sock into a sausage shape and tie five long pieces of string very tightly around each sock. Wrap each piece of string around the sock many times so that a 2cm section of the sock is covered in layers of tightly wrapped string.

Fill your bucket or bowl with enough cold water to cover the socks.

Mix and add the dye as per the instructions on the packet.

Put the socks into the dye and stir well. Use old wooden spoons for this and make sure that you wear rubber gloves because the dye can take days to come off your hands.

When your socks have been in the dye long enough, cut off the string that you have wrapped around them. You will see that these bits have remained white whilst the rest of the sock has been coloured by the dye.

Now give your socks a good wash.