I carry a small first aid kid; 15x15cm and 7.5×7.5 cm adhesive dressings, some gloves and two wipes and duct tape, all wrapped up in cling film and in the tool bottle.
If I need two bottles, it goes in the tool pouch in the back pocket.
Also:
Two tubes
Two CO2 (innovations nano)
Small multitool
Chain link
Topeak instant patches
Pump
Wet wipe
Money
Phone
For food:
Two gels
Something savoury
Banana
And a windshell/raincoat small enough to fold into the back pocket. Absolute waterproofness is not required.
Again, all this will fit in tool pouch in rear pocket.
When I say “tool pouch”, what I really mean is £1.99 clear pencil case from Rymans. The Lezyne equivalent fell apart.