curl --request POST \
  --url https://tryno.io/api/t/{handle}/pay/{slug}/upsell

const options = {method: 'POST'};

fetch('https://tryno.io/api/t/{handle}/pay/{slug}/upsell', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://tryno.io/api/t/{handle}/pay/{slug}/upsell"

response = requests.post(url)

print(response.text)

{}

{
  "error": "<string>"
}