These solutions are for a previous version of this task, where cola bottles were called chews and marshmallow twists were chocko bars instead.
Kaylee J sent us answers to the Puzzling Sweet Shop problem:

Rosie can buy:

one lollypop and one mini egg.
one chocko bar, one mini egg and one chew.

Are there any other combinations of sweets Rosie can buy? Let us know if you think there are.

Kaylee goes on to answer the rest of the questions:

Alice bought two mini eggs. I know this because this is the only combination of sweets which add up to 20p where she bought at least one set of every sweet.

James bought 4 chocko bars. I know this because it is the only sweet that has a price that can divide into 20p exactly when chews are not included.

Katie bought 2 chocko bars, one lollypop, and mini egg.

Henry bought one chocko bar, one mini egg, and 6 chews.

There may be some other sweets that Henry could buy too. Jessica suggests 4 chews and 4 mini eggs. I wonder if there are any other combinations?

During the 2020 Lockdown we had this solution come in from a pupil at St. Thomas' London

Thank you very much! This is a really good submission.