What are Samoan roadside stands selling in white styrofoam cups?

Question

I've just spent several days driving around Samoa, Upolu to be specific. There are stands by the side of road where people sell coconuts, greens, and any number of other things, most of which I could recognize. One day, a woman was standing very close to the edge of the road (I thought she was about to cross) with a cardboard box full of Styrofoam coffee cups. But there were no lids and I could see they were full of something black, with a small white thing perched on top.

Later, we came back the same way and she was still there, but her box was half empty. I realized she was selling them. I later saw them at many roadside stands. Here's a picture of one:

What is in these cups?

Answer 1

When these cups are seen next to coconuts, the proprietor is likely to be selling 'vaisalo', which is a smooth beverage made from... well, coconuts.

A corroborating image, which has been labeled is shown below...

Source: Vaisalo - American Samoa, fair use

In the absence of a label, the only way to tell the difference between vaisalo and 'koko Samoa' is by the colour of the beverage...

Source: Koko Samoa, fair use

Accordingly, 'koko Samoa' may also qualify for what you have seen for sale, and the young coconuts may be there for some other product.

Controlling reference...

Source: Lonely Planet Rarotonga, Samoa & Tonga