I watched for the person drinking it and embarrassingly asked for the can when they were done. It can still be hard to ask someone for their trash. But it's getting easier.
After it was cleaned up and at my house, I took a better pic. It's a Starbucks doubleshot energy drink in the form of vanilla-flavored coffee.
In the end, now I have one more person watching for interesting cans for me. It's worth the embarrassment.