This may seem like a strange question, but if you read this recent article on the MyLondon website you may be confused. The article explains how several pairs of stations are linked so that journeys are charged as one. In it the author asserts:
You must not touch anything else with your Oystercard or contactless payment method between exiting the first station and entering the second, so if you are tempted to stop for a coffee on the way, pay for that in cash or with a different card.
That advice is complete rubbish. You mustn’t use a bus or tram between the stations, but you can buy a coffee or anything else you fancy using the same card/device. TfL only get to see when you touch your card/device on one of their readers. They have absolutely no way of knowing what else you’ve used the card for at any point during the journey.
Incidentally, the article is supposed to be making known the hidden OSIs (out of station interchanges) that don’t appear on the rail and tube map. They link to the very user-unfriendly list on the TfL website, but you can find out about all of them on this site at our OSI List. They also don’t mention that some of the links shown on the rail and tube maps are NOT OSIs (eg Swiss Cottage to South Hampstead).