I posted in summer about this and other posters helped me realise my daily portion or two of gazpacho was causing the acidity.
Now it's back. I'm avoiding coffee. We did have raw tomato for breakfast yesterday but since then I can only think the causes might be... weak black tea mid morning today (I drink black tea really rarely) or a Fudge finger and selection box bag of Buttons shared with my husband last night? (Don't judge...Christmas eating "rules" are still in place in this house).
Any ideas? It's quite mild but still irritating.