Try to avoid all you can for two weeks and if it's going to work then you can start to incorporate some of forbidden fruits. Some people reported they don't have problem with coffee, but dark chocolate make them stutter worse, it's individual. Some types of teas are lower in tannins, milk chocolate has less tannins than dark for example. Maybe higher dosages can still work even with foods high in tannins... but you have to try it strictly for two weeks first. Good luck