Finding suitable souvenirs for office distribution (会社用バラマキお土産) is a problem of every Japanese traveller, but this article in Japanese has lots of tried and tested ideas for Beijing. To quickly summarize:
- China-only variants of Japanese candy, like banana milk or wine & chocolate Pocky. Even Chinese packaging of "normal" Japanese candy is unusual and interesting.
- Western-style pastries from Daoxiangcun (稻香村), Weiduomei (味多美), or Holiland (好利来)
- Red and green bean paste buns (紅豆焼, 緑豆爽)
- Chestnut jelly (栗子羹)
- Tea-flavored candied kumquat (茶香金桔蜜銭) and cranberries (紅茶蔓越苺蜜銭)
- Pineapple tarts (風梨酥), although this is more of a southern Chinese thing (no pineapples anywhere near Beijing...)
And one thing not to buy: guǒfǔ (果脯) preserved fruits may be Beijing's most famous souvenir, but they're way too sweet for the Japanese palate.
As an aside, the casual observer might look at the list above and sputter, "But most of those aren't really Chinese!" That's not the point: the primary purpose of omiyage is to show your respect your colleagues, and the secondary goal is that whatever you bring back is tasty and goes well with tea. Being "exotic" is, at best, number three on the list, and being so exotic that it interferes with goal 2 is not good at all.