It differs a bit between bikes, but for a long ride
Bike
1 x Tool Bottle
1 x Electrolytes Bottle
Helmet
Glasses
Gloves
Hydration Pack
Garmin
In Tool Bottle:
Spare tube
3 tyre levers (I can't do tyres without levers)
1 puncture repair kit (adhesive patches)
Multi-tool with chain tool
Chain quicklink
Cable ties
In hydration pack:
Water
Credit Card
£10 note
Phone
Spare gels
Mini track pump
Jersey:
Gels
Flapjack
Thin waterproof
2nd spare tube
I carry pretty much the same to commute, except only 1 innertube, and no electrolyte drink.
My wife commutes with a tool bottle, similar load out except no multi-tool and a CO2 pump with 2 x 16g bottles. Also, riding a Croix her inner tube takes up more room.