Every week a Guardian Money reader submits a question, and it’s up to you to help him or her out – a selection of the best answers will appear in next Saturday’s paper.

My local Waitrose says I have to bring my own coffee cup from next week. Two questions: which is the best reusable cup (some are more than £20!); and is this a ploy so that we don’t go in to get free coffee, as they are a pain to carry around?

Do you have a problem readers could solve? Email your suggestions to money@theguardian.com or write to us at Money, The Guardian, Kings Place, 90 York Way, London N1 9GU