Pentosin DOT4 LV or ATE SL6 are low viscosity fluids that I know.
BTW. called dealer and asked about change and was told " we change it if it is getting darker or at 40k". I asked about performing water content test like it is done in Europe. i was told "NO, we dont perform any tests" Every professional car service in Europe has brake fluid tester.... this is really third world country regarding infrastructure, vehicle safety, and maintenance. Ex. in Germany car will NOT pass inspection if brake fluid does not meet minimum boiling point of 180C (356F)
I told them I will change it myself after two years since 40k is way too long based on my driving habits, even Brembo recommends 2-3 years interval.