The cycle to wash towels on is the regular wash cycle.
However towels can also be washed on the normal cycle or cotton cycle.
The regular cycle is a good choice for washing most towels and the faster spin and longer wash time helps clean the towels of dirt and bacteria better.
The cotton cycle is a good choice for cotton towels.
If your washing machine has a heavy duty cycle or sanitize cycle it's a great choice for a deeper clean but harsh settings may also damage the towels.
Some washing machines also have a towels cycle which is made for washing towels.
If your washing machine has a towels cycle then it's best to wash the towels on the towel cycle.
When washing towels warm or hot water is recommended.
You should use a cycle specifically for towels or a normal/regular cycle.
A sanitizing cycle can also be used, but may not be recommended for every wash, depending on the towel fabric.
To get your towels really clean you can use 1/2 cup plain powdered laundry detergent.
Soak the towel and any other laundry in the tub overnight, and then run the laundry through the washing machine again with no detergent to rinse it out.
Dry as normal.
This is called 'laundry stripping' and it removes deep dirt and residue that ordinary washing doesn't get out.