Simple shell script that keeps re-configuring your iptables, or default route, or arp table, or something like that, in a pattern that breaks und un-breaks your network connection without dropping any sockets.
Just break it for 1 second at a time at ever increasing frequency.
Alternatively, if you can use the web client, open up developer tools in a Chromium-based browser, go to the network tab and click the drop-down menu that says Online. Add a few custom profiles with limited uploaded speeds and high latency and cycle through those as needed.