Try this: Tea and the Guillotine
What is a popular flavored tea that would be enjoyed in France?
China teas are liked - Oolong and Lapsang for example. Green tea is increasingly used.
Chamomile tea is something that is very typically French - often just called a tisane.
There is a large community of North Africans, so mint tea is found, and there is a cherry tea.
I'm not sure there is a particularly preferred flavoured tea. I would choose one that you think fits with your character(s).