Recently, I was listening to a talk at a conference. The speaker told us how he had his students do something-or-other because it was fun. He specifically mentioned that he wasn’t too concerned with what students learned, as long as they had “fun”.
Your students may find it interesting to compare the acid content of a low-acid apple juice or a low-acid orange juice to that in a regular juice of the same brand. These sample types could be added to an existing acid-base titration experiment, form the basis of a new experiment, or be used as project topics.