If you plant Southern Highbush, that won't be necessary; there were developed at the University of Florida and require little, if any, chilling.

The ice cubes won't help. It's the leaf and flower buds that need chilling not the roots.

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.

An old refrigerator might work.Take out the shelves and drawers and keep it about 40F for a few weeks. Brady

Brady:

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.