curl --request PUT \
  --url https://realtime.replace-me.example.com/custommeters/{customMeterId}/meterreadings/{meterReadingId} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "timestamp": "2020-01-04T19:00:00.000+0000",
  "value": 13
}
'

const options = {
  method: 'PUT',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({timestamp: '2020-01-04T19:00:00.000+0000', value: 13})
};

fetch('https://realtime.replace-me.example.com/custommeters/{customMeterId}/meterreadings/{meterReadingId}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://realtime.replace-me.example.com/custommeters/{customMeterId}/meterreadings/{meterReadingId}"

payload = {
    "timestamp": "2020-01-04T19:00:00.000+0000",
    "value": 13
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.put(url, json=payload, headers=headers)

print(response.text)