Compare modern Starbucks and similar emporia with Victorian coffee houses. There is plenty of information on these at www.victorianlondon.org and look under "Food and drink".
Students may find it easier to learn the skills of source analysis in one context and then apply these skills to the context of their history course.
A visit to the websites of coffee sellers such as Starbucks (www.starbucks.com), big manufacturers such as Nestle (www.nestle.co.ukProductNewsAndOffersAboutOurBrandsBeverages) or campaigning organisations such as Global Exchange (www.globalexchange.orgcampaignsfairtradecoffee) would give students the opportunity to compare different presentations on a familiar subject.
They could then compare contrasting views on an historical subject matter and look for differences in the same way.