Commonly found variants; note these may range from acceptable alternatives to non-standard forms or incorrect spellings*.
* Singlish is a largely spoken creole, and as such descriptivism (recording forms that reflect actual pronunciation in spoken language, or as appearing in the linguistic corpus) is more pertinent than strict prescriptivism. Nevertheless, the use of more standard forms (or for words originating in languages with Latin script, such as Malay, accurate to the original spelling) is recommended and encouraged.

also can:

goo yoo guyu gooyoo gu you goo you

gu yu

Hokkien:

牛油

poj:

gû-iû

expand for details Detailed etymology

definitions

noun

  1. butter
  2. All I had for breakfast was some leftover chiam tao lo ti with gu yu.

  3. (attributive, drink ordering, usually only with kopi) with a slab of butter melted in
  4. The traditional kopi gu you is made with Nanyang Coffee. This is a local coffee made in Singapore with robusta beans that are roasted to Full City with added sugar and butter or margarine.

    — 2023 August 28, Azlin Bloor. Singaporean and Malaysian Recipes, "Butter Coffee (Kopi Gu You)". https://www.singaporeanmalaysianrecipes.com/butter-coffee-kopi-gu-you/

    I had to try the shop's signature kopi gu you (S$1.20), an intriguing combination of butter and coffee with condensed milk ... Contrary to the cloying rich taste I expected, the peculiar concoction tasted surprisingly light, and the butter gave it a delightful creme brulee-like taste.

    — 2016 June 11, Rachel Kwek. Today, "Five kopi joints where you can get your morning cuppa". p.23