I just posted a list of foods (IC Diet) that may cause flare-ups or discomfort for persons with IC. Just keep in mind every person is different so what bothers me might not bother you. Since this list should be customized to the person, I would recommend keeping a food diary for 2 to 3 weeks. In addition to listing what you ate during each day, I would also write how you felt after each meal. Also, pay attention to the brand of the food items. Some brands you may not have a problem with consuming.
There is a product that you can buy over-the-counter, usually available at a pharmacy, called Prelief. Prelief helps to reduce the acidity of foods you consume. If you take Prelief before eating or drinking, you may be able to add that food or drink item back into your diet.
Another important item is taking vitamins and/or supplements. For instance, magnesium makes my bladder spasm like crazy. If you have trouble with certain vitamins or supplements, try to see if you can get those same nutrients through food rather than a pill or tablet.
A lot of IC people find that certain teas are beneficial. Marshmallow root tea is a product that IC people recommend. I did try marshmallow root tea, and I found I had no problems with that particular tea. I will research and post a list of teas that other IC people are recommending.
Let me know if there is a tea or supplement you find helps with IC symptoms. Please feel free to comment and/or follow my blog!