My drug of choice for colds is NyQuil. It's always been great for opening up my nasal passages enough to let me breathe easily and then knocking me the fuck out so I could sleep off most of the cold. I remember several years ago when all of a sudden NyQuil stopped doing anything useful. I had no idea why but I directly observed that it was like it had been replaced with a non-functioning placebo. Only a couple years…
Original NyQuil also had a healthy shot of ethyl alcohol in it. Exactly the thing you weren't supposed to mix with pseudoephedrine.
So a small amount of alcohol won't really have much of an effect, I'd claim.