I live in Brazil and here our winters are too mild.
If I put ice cubes on the soil during the winter nights, do you think I can trick my blueberries into thinking that they are getting more chill hours?

The roots would get colder with the ice on top of the soil, but the leaves and stems would not feel the ice... Will it work if only the roots get cold and the leaves and stems don't?

Some of the SHB need little chilling but I won't agree that they need none. Sharpblue has the reputation for needing almost none. Biloxi and Snowchaser are also very low chilling and do well if grown evergreen, meaning they keep their leaves all winter.

That's an idea I've had for off season blueberry production. A chest type freezer with lid on top can be converted to higher temperature controls to maintain about 5C. A person could fit about 8 small potted blueberries in a large freezer and produce berries 12 months of the year in the tropics. The same plant could produce a crop about every 8 months. With enough plants on different schedules anythings possible.

Two weeks chilling at a constant 5C is all it would take for the low chill SHB.