I have a fairly persistent problem with "sloshing" sounds when running. Specifically, on the downbeat of each step, I get this feeling and sound like there's fluid being dropped suddenly. It's annoying, and eventually starts to interfere with my running since my stomach starts cramping and I start feeling like I need to find a bathroom (although, in actuality, there often is nothing to discharge). Poking around on the internet, the general consensus is that it's a factor of too much fluid in the stomach, and the way to solve it is to drink less when running. However, a) that doesn't do much good if it starts after I've been running for several minutes and b) it doesn't feel like it's at stomach level, but lower down on the body and more toward the back. It doesn't always happen, although I've found that it's a bit more common at times when I'm having one of my days-long borborygmus incidents (and yes, I've seen a doctor on that, and they basically shrugged and said it didn't seem harmful).
Keeping my core tensed seems to help, oddly enough, but that's tiring to do for several minutes at a time. Other than trying to drink less fluids during the day (I'll often down a fair amount during the day, although I try to avoid drinking too close to running for fear of cramps), is there anything I can do?