You can have a alternative of cron jobs solution by implement you function in a file (eg: /very/secret.php if your jobs need to be secure, make sure the function can be call only when it get the right parameter eg: /very/secret.php?key=long-random).
Then use some free cron job server on the web like: https://www.easycron.com/ or https://www.setcronjob.com/ (just do a web search for "free online cron jobs"). You give them your URL and some configuration and then your jobs will be executed by them at a specific time of day.