[Updated March 1, 2012]
Many of you may already know I'm from the Pacific Northwest of the U.S. (Greater Seattle area), the birthplace of coffee shop giants Starbucks and Tully's. As much I also particularly enjoy small, mom-and-pop cafes, there's just something about the sight of a Starbucks or Tully's that brings me a bit of nostalgia and comfort.
My nearby Starbucks (well, all four of them...) has been particularly inviting for me the past couple years, given that it is non-smoking and offers wireless internet service so I can sit and type away while sipping my soy matcha tea latte. (Note: Not every Starbucks has wifi...)
So if you have allergies, or a specific way you like your drink, rest assured it is possible to get these customizations. If you are a coffee fanatic and prefer your latte grande-nonfat-triple-shot-decaf-foam-extra-hot, this is possible, of course, but I wouldn't say it's common in Japan, at least compared to the U.S. Especially considering Starbucks.com has an interactive tutorial on how to order a drink...
"トールソイ抹茶ティラテ" (to-ru soi matcha ti r(l)ate, tall soy matcha tea latte) and of course, finish with a nice お願いします (onegai shimasu).
The nice thing about the menus at Starbucks or Tully's is that they are listed primarily in katakana (the names/sizes/etc.), which makes ordering easier than say, ordering food at a traditional Japanese restaurant. Although, I have been to stores (usually in Tokyo or larger areas) that are quick to offer an English menu (of course, if you look foreign and they assume you speak English).
Both Starbucks and Tully's Japanese websites have information on how they can customize, all in Japanese of course.
So here are the words you need to know if you want to customize:
how to customize your drink at Starbucks or Tully's in Japan
|Low-fat milk* (dairy)||低脂肪乳||ていしぼうにゅう||teishibounyuu|
|Fat-free/skim milk* (dairy)||無脂肪乳||むしぼうにゅう||mushibounyuu|
|Whip cream||-||ホイップクリーム||hoippu kuriimu|
|Foamed milk*||-||フォームミルク||fo-mu miruku|
|Extra hot||温度熱め||おんど あつめ||ondo atsume|
Shots, syrups, and sauces
|Extra espresso shot||-||エスプレッソショットの追加||esupuresso shotto no tsuika|
|White mocha||-||ホワイトモカ||howaito moka|
|Chocolate sauce*||-||チョコレートソース||chocore-to so-su|
|Caramel sauce*||-||キャラメルソース||kyarameru so-su|
|Chocolate chips||-||チョコレートチップ||chokore-to chippu|
*Note: Almond syrup, the flavored sauces, low-fat and fat-free milk are not available at Tully's, according to their website, but if you've gone and had no problems getting any of these, feel free to share. I also did not see an option for foamed milk or extra hot, but I'm sure you could ask the barista to do either. Tully's DOES, however, offer the addition of ice cream (アイスクリーム, aisu kuriimu) or matcha (抹茶, まっちゃ).
*Most customizations cost an additional 50 yen, though some, (i.e., extra hot, chocolate sauce) do not.You can also ask for more or less coffee in your beverage, though decaf isn't something you'll see on the menu.
And! If you bring your own mug (tumbler or otherwise) to Starbucks, you can get a 20 yen discount off the price of your drink. Instead of asking for a traditional size, say "パソナルカップ" (pasonaru kappu) or "パソナルサイズ" (pasonaru saizu).
Final note: When you order at Starbucks, depending on which one you go to, they occasionally ask if you want a マッグ (maggu) or カップ (kappu). Mugs are typical mugs, (better for the environment if you're just going to sit and drink your latte), while cups are the typical paper cups. I haven't been asked this at Tully's before, so if you have, feel free to mention it below.