Take all essentials you might need
The shops in Cuba are universally dreadful. Trade embargoes have blocked many common brands and those that do make it through are very expensive. The result is a very narrow selection of practical products. Bring all the essentials you might need with you – toiletries, sun block, insect repellent, camera cards etc. – as finding these items will be nigh on impossible if you’re out of a major center.
Food is no better. Stores sell bottled water, sometimes biscuits, the occasional packaged products and rum. Trying to put together something like a sandwich for lunch on the road will be a real struggle. So, if there is something snack-related that you can’t live without, it’s best to bring it with you. If you need the occasional bite of chocolate, stuff some in your backpack. Fancy a cup of tea? Pack those tea bags.