Edit in JSFiddle

var thngId = '5357ac4be4b0eec2cc69487c';
var propertyName = 'cmd';
var property = [{'key' : 'cmd', 'value' : 'espresso'}];
// DO NOT DO THIS IN PROD! This discloses your secret API key, instead
// work with run-time delegated auth, see: https://dev.evrythng.com/documentation/api#apps
// and https://github.com/evrythng/evrythng-js-sdk for examples.
var apiKey = ''
$.ajax({
    type: 'PUT',
    url: 'https://api.evrythng.com/thngs/' + thngId + '/properties/' + propertyName + '?access_token=' + apiKey,
    data: JSON.stringify(property),
    contentType : 'application/json',
    accept: 'application/json',
    success: function(data) {
        $('#result').html('Just ordered ' + data[0].value);
    }
});

<p><div id="result"></div></p>