Like you I can eat fruits and juices all day until that one oily or fatty food.
Yep, I have issues when combining sweet foods with ay food that has even modest amounts of fat. My head spins, I get brain fog, can't concentrate, tired.. It never made my AS worse (even before going in to remission), but it would give me proctitis (itchy bum). So yep I would say sugar + fat = pro inflammatory.