Taiwanese (not Mandarin).
You can hear these looping ad recordings everywhere, not only from stall cart vendors. There are vans that go around looping recordings advertising their NT$299 all-you-can-eat hot pot dinners, facials, massages, karaoke bars, election candidate, etc. The back part of the van is decorated with images of the product.
Anyway, the recording in this podcast is from a 山粉圓 drink stall. I've been hearing this recording ever since I went to the weekly Friday night market in Liu-Cha for the first time in September last year. I don't know what 山粉圓 is in English. It's some kind of little transparent ball-shaped thing served inside a really sweet beverage. No, it's not the "pearls" in "pearl shakes".