Snoring is usually a condition and a symptom of obstructive sleep apnea. This causes the airways to be partly blocked preventing the passage of air into the lungs. One treatment option to this is surgical procedures to reduce the degree of excess tissue in the airway. You can consult a doctor for more medical options.
There aren't any over-the-counter medications that he can safely take to treat this. Ask his doctor to have a conversation with him. Sleep apnea can increase your husband's risk for further heart problems. If he won't listen to you, and if he doesn't care that he's disturbing you, maybe he'll care that he's jeopardizing his own health. I've heard of men with apnea who sew a tennis ball into the back of their pajama tops, to keep themselves from sleeping on their backs. That trick does seem to reduce the snoring, but if your husband won't sleep in anything he thinks is uncomfortable, then he probably won't be willing to try that. Talk to his doctor. Good luck!