(((€2M @ 5%) / 365) * number of days in month) * 80% (to allow for 20% DIRT)
assuming that you were withdrawing the interest each month and not compounding it. e.g.:
c. €6,800 net of DIRT for January.
For a sum of €2M you should try to negotiate a special rate. Some standard accounts on offer have upper limits of €1M or maybe even less in some cases.