Your gut microbiome has changed since then I imagine. If you stopped eating fruit then whatever gastrointestinal flora that subsisted on it to survive probably decreased substantially. That could change how your body reacts to a reintroduction of something you used to eat before.

Your body also gets used to things if you eat them often. If I cut down on sugar for a while then eat it again I find my body reacts a lot more strongly to it than if I eat it regularly.

I used to drink 4x4 coffee a long time ago (4 sugar 4 milk) and that felt normal to me. I stopped doing that and quit cold turkey for about a year (switched to plain tea) and when I tried my usual 4x4 again it tasted cloying sweet and made me feel a little sick even.

I could probably work up to drinking it comfortably but even though I drank it for years before every day I couldn’t suddenly start up again.