I would urge anyone with anything infectious not to fly, but if you absolutely must, maybe consider the following.

Avoiding some wines helps. I'm not joking - some wines give me terrible sneezes, and worse if I have a cold. I do not usually touch wines nowadays but it honestly helps if I don't drink wine when I have the sneezes.

But then I suspect vodka and other liqueurs actually suppress sneezing, or maybe it's only an excuse for me .

If you suspect you might have a touch of hayfever mixed in, loratadine may help. It's not a remedy for cold, but an antihistamine that will help with hayfever etc. As far as I know, there is no over-the-counter anti-sneezing pills but there are some general remedies for cold. Whether they are any good or not is open for debate though.

Wear a surgical mask, even if it's just to warn other passengers and to encourage them to stay away from you

Pseudoephedrine or phenylepherine (Sudafed) with ibuprofen should help with ear pain you may get on descent.

Also please do your best to shield others from your sneezes (and coughs if you develop it), and please don't be a sniffler who sniffles loudly every 30 seconds like the passenger I had nearby recently. It's not very nice. Take lots of tissues and dispose of them sensibly in a plastic bag please And please try not to get bugs on your hands and touch other surfaces that others may touch shortly, just to reduce the likelihood of germs spreading!