The cube in a dream stands for prosperity and material factors of your life and what role it plays in your life. The dream could also show your very rigid views towards some issues.
Dream dictionary: Cube dream meanings
If it is full of dirty water, then it indicates family problems and trouble. If the water is clean, then it announces family happiness.
…In the dreams to see dice or play with small cube, which having a different number of spots on it indicates your risky personality. Maybe you are taking chances and playing with fate. The dream may also be a sign of unpredictable and potentially dangerous situation or relationship. It there isn’t such thing in your life now, then dream can foretell that in the future dangers can come….