So, lessons learned? Bring bigger sweets, with more eye-catching designs, including a clear call to action, and which are sugar-free and inedible.
Typical tech-guy reaction! xD
I think the obvious lesson is: Just grab any bag of sweets and go for a chat.
You say it yourself:
It can be a bit intimidating to go up to strangers and say "TALK TO ME". But saying "Hello! Would you care for a sweet?" is a socially acceptable ice-breaker.
The printing didn't matter.