Has anyone found an anti-snoring method/device that really works?

My husband snores, a lot... He is a mouth breather, which causes more snoring, when he rolls onto his back it is the worst. He doesn't just stop breathing like with apnea, but sometimes his tongue falls back in his throat cutting off his breathing momentarily, so he adjusts, and then is soon snoring again! We've tried the sprays, mouth rinse, breathing strips, humidifiers, herbs, everything affordable. I don't want to invest $50-$100+ into a device and then have it not work. Any advice?