I was making a cup of tea this morning, and I offered to make my new team mate one. She said yes, so I made our cups of tea, and gave it to her. A few seconds later, she walked past me, poured about 3ml of extra milk into her cup, and walked back to her desk.
This is the height of rudeness, and she has broken the code. When someone makes you a cup of tea (or similar), even if it isn't to your exact preference, the polite thing to do is to drink it anyway - it's not that far off, it's just a cup of tea ffs. I'm less inclined to offer with that sort of attitude.
Also, people who put like four heaped tablespoons of sugar in their tea. What are you, twelve years old? If you want a candy stick, just get one.
People who drink energy drinks like Red Bull: it tastes foul and smells like a combination of petrol and piss. Stop it.
Should probably mention something about shandies.