Today there is firmware update (0603) available for SugrCube so I came up with clicking the upgrade button in iPhone App. After downloading, installing and restarting (automatically) and the equalizer in iPhone app works now.
So now you have options to enable or disable 'Equalizer' in the app. Currently you have 2 pre-defined EQ to use: One is called 'Crystal Clear' and another one is 'Magic Bass'. As the name implies, 'Crystal Clear' reduces Bass and High but enhanced the middle range; 'Magic Bass' gives you more 'boom boom' emphasis.
It is nice to see Sugr Team is still working on this project after the KickStarter product delivered and kept their word.