Soybeans and soy products CAN be sources of oligosaccharides, especially of GOS (some fructans, too). But not all soy products are significant sources. If you know two things about fructans and GOS you will be on your way to understanding which soy foods you can include on your low-FODMAP diet.
I certainly don't agree that everyone with IBS must avoid all alcohol. There may be some adult beverages you can enjoy in moderation. Let's really zero in on FODMAPs.