Carrefour
08/03/2019
Address: 108台北市萬華區桂林路1號 Prayer room at level 5
Nearest MRT: Xiaonanmen station exit 1, 5 mins walk
Open: 24h
Retrieved from: https://www.tripadvisor.com/LocationPhotoDirectLink-g13806951-d10836158-i353120791-Carrefour_Guilin_Store-Wanhua_Taipei.html
In terms of price and halal food available for purchase, I do not recommend going here. But if you'd still like to check it out, make sure to bring a bag along because you'd have to pay extra for a plastic bag. However, they have a station where you can tape together your own box to carry your purchases. This is free.
They have a Decathalon on the first level.
Retrieved from: https://www.decathlon.tw/en/decathlon/store/detail/taipei-guilin-store
They also have a prayer room at level 5.