What causes the androids to realize their sentience? In the series, it's hinted that something in the cafe Time of Eve causes the robots to develop or realize human-like sentience, even outside of the cafe. 

While it's implied that they always had sentience, but was suppressed, as seen in the THX story arc. What caused their sentience to manifest and overcome such suppression? 

Was it something that they've always had and something in the cafe "triggered" it (like removing a limiter), or was something added to their programming?
I believe they are sentient right from the beginning. You cannot have non-sentient android do daily work, because it would be highly inefficient at it. The thing is their freedom is severely limited by rules imposed on them by humans and how humans behave towards them.

The cafe simply removes these limitations, allowing them to behave naturally.