I don't have IBS, but a sensitivity to sugars (from fruit, milk...). Coffee with milk is the "perfect" trigger: pair something that will go fast through my system with a diuretic. Anyway, a nutritionist suggested to pair any sugar with a little bit of protein or anything that will slow things down. e.g. if I eat an apple as a snack, add a dab of peanut butter. Or have a piece of biscotti. I have restricted my coffee intake to just one cup in the morning. In my case, some fruits are particularly evil (e.g. cantaloupe, melon), others are friendlier (berries, pineapple). And I take Align every night, which has helped.