AOA brothers. This problem of tuk tuk or tik tik has been a pain in the b_m for many years for me. I owned an altis cruisetronic from 2012-2017 with an automatic transmission. This problem persisted for about a year until i found a solution to this. The same as many guys suggested, I changed the discs, the brake pads (genuine) and what not but the problem still persisted. The solution was very simple .... there are small metal pins/clips (also known an anti-rattle clips in north america) which keep the brake pads to their place and control their antero-posterior movements during braking. These clips are flexible and loosen up with time, we need to take them out, clean, expand them (in local terms, use a screw driver and inko kholna hota hai). re-insert and tighten the shims over brake pads and put back, cover with caliper. As suggested above, the grease can also be applied.
This solved my problem for at least 5000km and had to be repeated because the auto garis do have this tik tik of some sort. I dont have the exact pictures of those clips, but they look like this somewhat. Plus, I had a corolla, you might have them in vitz too. Principal for both cars should be the same.