I suspect one could use parts from an old microwave and a copper cup like these to craft a directed energy weapon that would fry the 5g and Wi-Fi receivers as well
Probably not 5G, microwave ovens operate at 2.45 Ghz, in the unlicensed ISM band. Cellular is all on licensed frequencies and their recievers have notch filters to block all the ISM noise.
You could definately interfere with 2.4Ghz wifi.
Be careful poking around inside a microwave, you can get a 5000V shock if you touch the wrong thing.