Got an email from a cafe thanking me for my visit

The problem is...

I have never given them my email address :blobcatfearful:

How did they know that I entered their cafe? And how did they know to EMAIL ME?

I didn't even pay for my drink, my friend did, so it's not like they could link my payment card with my email address somehow

And even if I did pay with a card, there is no point in the entire transaction where I would need to hand over an email

What is this really weird and creepy surveillance?