Nearly all bubble tea sold in markets across the country exceed the recommended upper limit of the daily sugar intake recommended by the World Health Organisation (WHO), the Foundation for Consumers warned on Thursday.

The watchdog tested samples collected from 25 brands in May, including ones with tapioca "pearls" for sugar levels and found that almost 100% of the samples had an excessive amount of sugar. It also added that eating too much sugar could lead to weight gain and other health problems.

The agency said it collected its samples under the criteria that they were all the same regular size with no ice and with each cup priced between 23 baht to 140 baht. The samples were taken for laboratory testing to check for calories, sugars, fat, and heavy metals like lead and preservatives.

The result showed that only two brands - KOI Thé and TEA 65° - had an amount of sugar per glass lower than the recommended upper limit of daily sugar intake as recommended by the WHO. However, the test did not cover the entire bubble tea market in Thailand which has hundreds of brands.