Occasionally when the thongs are brand new, they can squeak if some sweat develops underneath the foot. The problem should go hopefully away once the thongs are worn in and some of the initial sheens wears off. The thongs almost always squeak when wet such as after swimming whether they are brand new or well and truly worn in.
However, once the thongs are worn in, under normal circumstances they should not squeak during normal walking (unless they get wet).
If the thongs are squeaking with normal walking (they are not wet), there are two most common causes:
If your thongs are squeaking and it’s not because they are wet, then we suggest:
Washing them in warm water and give them a vigorous scrub with a scrubbing brush or green scourer then thoroughly drying them with a towel.
We often find that when this happens the thongs have somehow come in contact with something (we don't know exactly what) and washing and drying them often fixes this!
If the thongs continue to squeak during normal walking, after they have been well worn in and after you have vigorously washed them, normally ‘roughing up' the surface of the thong with some coarse sandpaper fixes this.