On a 38-degree afternoon in Hanoi or Saigon, you'll spot vendors pushing carts loaded with clear bowls of wobbling, translucent jelly. That's "bot san day" — a drink made from the starch of the san day vine (Pueraria thomsonii, a cousin of kudzu), set into a soft gel and served cold with sugar syrup and a squeeze of lime. It's been around for generations and doesn't get much press, but regulars swear by it.
What It Actually Is
"Bot san day" translates loosely as san day starch powder. The root is dried and ground into a fine white starch, then dissolved in water and cooked until it sets into a pale, slightly bluish-grey jelly. The texture sits somewhere between silken tofu and aloe vera gel — smooth, barely firm, and cold from the fridge or a bucket of ice.
In traditional Vietnamese medicine, san day starch is considered a "cooling" food — meaning it's believed to reduce internal heat, soothe the throat, and help the body cope with hot, humid weather. Whether you buy that framework or not, a bowl of cold bot san day on a sweltering afternoon does the job. It's hydrating, light, and about as far from heavy as a snack can get.
How It's Served
The standard street version comes in a plastic cup or small bowl. The vendor scoops out a portion of jelly, cuts it into rough cubes or scrapes it into thin ribbons with a spoon, then pours over a light simple syrup — sometimes plain sugar water, sometimes infused with pandan for a faint grassy sweetness. A few drops of lime juice go in last. Some stalls add a spoonful of "hat e" (basil seeds) that bloom into translucent spheres, or a few pieces of "thach den" (black grass jelly) for contrast.
Prices run 10,000–20,000 VND per cup depending on the city and whether you're at a fixed stall or a roving cart. It's not something you'll find on restaurant menus — this lives firmly in street food territory.
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Where to Find It
Bot san day is a nationwide drink but you'll encounter it most reliably in a few specific contexts:
Hanoi
In the Old Quarter, look around Hang Be Market and the lanes off Hang Ga in the morning and early afternoon. Dong Xuan Market has a few permanent stalls selling it alongside other chilled starch drinks. It's also common in residential neighborhoods outside the tourist corridor — anywhere with a cluster of drink carts near a school or market.
Saigon
In Ho Chi Minh City (호치민시 / 胡志明市 / ホーチミン市), the drink is popular in Districts 5 and 6, where it often appears alongside "tau hu" (soft tofu) and other Teochew-influenced sweet soups. Ben Thanh Market's surrounding streets have vendors selling it from coolers in the late morning. Street carts near university campuses — around the Binh Thanh and Thu Duc areas — tend to keep it in stock through the hot season.
Da Nang and Hue
Both cities have a version, sometimes called "nuoc bot loc" locally, though the preparation is nearly identical. In Hue especially, it fits naturally into the city's culture of light, finessed snacks — you'll find it in the morning market lanes near Dong Ba Market.
Everywhere else
During summer months (roughly April through September), bot san day carts pop up near beaches, parks, and pagodas across the country. If you're visiting Hoi An in the heat of the day, keep an eye out near the market on Tran Phu.
When to Drink It
Morning through early afternoon is when most vendors are set up and the jelly is freshest — made the night before or early that morning, kept cold. By late afternoon, many carts have sold out. If you're planning a day of walking — through Hanoi's Old Quarter, around Hoi An's old town, or along the Saigon (사이공 / 西贡 / サイゴン) riverside — stop for one around 10am or 11am before the heat peaks. It won't fill you up or slow you down.
It also pairs well with a break from heavier food. If you've just had a bowl of "bun bo Hue (분보후에 / 顺化牛肉粉 / ブンボーフエ)" or a plate of "banh xeo" and want something that won't compound the heat, bot san day is a reasonable palate reset.
Photo by Nguyễn Thị Thảo Hà (Ha Nguyen) on Pexels
Making It at Home
Bot san day powder is sold in most Vietnamese dry goods stores and some Asian supermarkets abroad — look for small packets labeled "bot san day" or "Pueraria starch." The ratio is roughly 1 part starch to 8–10 parts water. Dissolve the powder in cold water first, then heat over medium while stirring constantly until the mixture thickens and turns from cloudy white to translucent grey-blue. Pour into a shallow tray and refrigerate until set, about two hours. Serve with sugar syrup and lime.
The one thing to get right is the sweetness balance — the syrup should be light, not cloying. The jelly itself has almost no flavor, so the lime and sugar are doing all the work.
Practical Notes
Bot san day is one of those drinks that's easy to walk past if you don't know what you're looking at — the pale grey jelly isn't exactly eye-catching. Ask vendors for "mot ly bot san day" (one cup of bot san day) and they'll know exactly what you want. Allergy note: it's gluten-free and dairy-free by default, though some vendors add condensed milk as a topping, so it's worth checking.
Last updated · May 26, 2026 · independently researched, never sponsored.
