I once heard Sheena Iyengar relate an anecdote about her difficulties ordering green tea with sugar in Japan. The waiter and manager refused to bring it to her, because drinking green tea with sugar is just not done in Japan, and they felt it their duty to protect her from making such a baffling and unseemly consumer choice.
It's a choice however that most in the West take for granted. Growing up in Australia in the days before expresso machines were everywhere, serving and ordering tea or coffee was pretty simple. You ask someone if they want milk or sugar (or serve the drink black with the milk and sugar on the side). Those were the only variations. Today it has become a somewhat more complex affair (you might find someone asking for a decaf soy milk flat white, for example), but one standard assumption still remains. Sugar is served on the side, not in the drink. Or if it is, your host will have first asked you whether you want sugar and how much.
But it's important to remember that this assumption is not shared all over the world.
I was in Malaysia recently, and as I am prone to do, I had eaten too many delicious Malaysian sweets that day. So I hankered for something cleansing and slightly bitter to counter my sugared-out feeling. Sitting down at a cafe, I ordered teh O, which is what they call black tea in Malaysia. To my surprise, it was full of sugar - the standard way of serving it. I was informed that for sugar-free tea I had to order teh O kosong (kosong meaning "zero" or "empty"). In the traditional Malaysian coffee shop, rarely is there sugar on the table - it is already in your drink unless you state otherwise.
The same places also served Chinese tea, but by contrast, it is always served without sugar. Which is quite right, too; I've never known anyone to drink Chinese tea with sugar and this seems like a very wrong thing to do, somehow. Although truth be told I'm sure it would actually be quite nice.
Chinese tea and black tea are not all that different, really. Which is why it was odd that the default assumption was that one should never be served sweet and the other should always be served sweet.
So what happens if you just order "tea" in Malaysia (teh)?
Then there's teh tarik and teh halia and teh ais and so on, but that's a whole 'nother story.
When I was younger I travelled with my parents to various places in Indonesia, and visited family friends at their houses. Almost without fail, the hosts would serve us tall glasses of hot tea of the fragrant local variety. At the bottom of the glass was a substantial quantity of sugar - perhaps 3 teaspoons worth, or more, I couldn't really tell. A teaspoon was either left in the glass or available nearby.
I would stir the tea and drink it down as was polite - it's pleasant but very sweet, as you'd imagine; and soon enough we would depart to visit another household, who would serve the exact same drink. Now if you visit 4 or 5 people in a day, and then do it all again the next day, pretty soon you're consuming a whole lot more sugar than you need to. By the time we left Indonesia, my teenage acne was a little out of control, and while the humid weather may have had something to do with it, I blamed the sweet tea.
I complained to my mother about how the amount of sugar Indonesians put in their tea was ruining my complexion, and by extension, my adolescent self-esteem.
Her response: "So why did you stir the sugar into it then?"
Good question. I just assumed that was what you did. The sugar was in the glass for a reason, right? And if sugar is just sitting at the bottom of a tea-filled glass, it's just asking to be stirred, no?
But the proper way was obviously to stir "to taste". If you want it really sweet, stir all the sugar in; if you just want it a little sweet, stir just a little.
Likewise, my first time ordering coffee at a Malaysian-Chinese coffee shop resulted in a thick bitter brew with no apparent milk or sugar... until I got to the bottom of the cup, and discovered a thick layer of sweetened condensed milk waiting for me. Where I come from, it would be almost unthinkable for a cafe to serve coffee or tea with 2 sugars already added, and it puzzled me that this was such a common practice in Malaysia.
Yet, it's just about knowing the rules, and everyone in Malaysia knows them. I'm sure a lot of Malaysians would tell me, "If you didn't want sugar in it, why didn't you order it without sugar?" Which, objectively, is not an illogical question.
The guide to ordering food in Malaysia
"Egg tea" in Indonesia
Is chai latte only a drink for wankers?
Green tea is intent on world domination
Filipino iced tea and other hard drugs