For shorter rides I use a small saddle bag with an inner tube, self adhesive patches, multi tool, cable ties, AA batteries (Garmin), pliers, short segment of chain (usually the excess from when i last changed), a spoke string thing and a pen, oh yeah, and a face mask and hand gel (new additions from 2020!). I've been meaning to add a cleat bolt as someone mentioned earlier (you would think I would learn from the consequences of a lost bolt from an SPD!). A small pump lives on my bike (that needs upgrade). Phone, card and a tenner are normally in my pocket along with a couple of cereal bars and some fruit. Longer rides generally mean changing to a larger saddle bag to include more food, some warmer clothes, hand gel and a jacket of some kind and possibly spare batteries for the front light, powerbank and associated cables for phone and rear lights and head torch if I'm going to be riding overnight.