I often have this happen and also food want to, ahem, come up, when riding. Sigh, my digestive system, which I used to be able to so take for granted, seems to be more finicky as I get older. For this reason I try to eat breakfast a couple of hours before an am ride, and to stick with gels or liquids. Few energy bar type things work, although the Larabars so far might be OK. I have had to experiment to find those that will stay down. Just listening to the body to see what might be happening.