For me, I pronounce it in two ways.

1. /ˌaɪˈtɑːk·ki/ - US's accent
2. /ˌaɪˈtɔːk.ki/ - UK's accent

There are three syllables to be pronounced:

i.e. 1. like the I letter - 2. talk with stressed - 3. like ky in milky

いたっき is how i pronounce it, or in english i'll add an l, " ee-(talk)-(key) (^^)

For people who are non-native speakers of english, its doesn't matter. Because we just write it when trying to login and no need to pronounce it.