Serious Eats - seriouseats.com

My girlfriend recently had lunch at a restaurant. There were four people in the party. One of them didn't want water, and one person finished his water very quickly. The waitress actually poured the water from the one glass to the other.

After they...spoke...with the waitress for doing that, she took both water glasses back to the counter, just as two new customers entered, and sat at the counter. The waitress took the two dirty glasses, and gave them to the new customers.

Thankfully, my girlfriend and the rest of their party saw this, warned the two new customers who promptly left the restaurant, and they spoke with the waitress again, and then left as well.