My suitcase for Rio: what I would actually bring
I would pack for a city where you can go from the beach to the metro, enter an air-conditioned museum, walk a lot and end the day watching the sunset. That is why I prefer lightweight clothes you can mix and wear again rather than filling a suitcase “just in case”.

Clothes for the heat

Bring breathable T-shirts or tops, shorts, dresses or lightweight trousers and quick-drying underwear. Summer humidity can feel intense, so a small spare change of clothes in your backpack can save the day.
A light layer even in summer

The metro, shopping centres, restaurants, museums and vehicles may have strong air conditioning. A shirt, very light jacket or scarf takes little space and prevents you from feeling cold when you arrive sweaty from outdoors.
Beach
Swimwear, sunscreen, sunglasses, a cap or hat and a bag for wet clothes. I would not take unnecessary expensive items onto the sand. If travelling solo, decide beforehand what you will do with your belongings when you enter the sea.
My advice: in Copacabana, I usually recommend Barraca Rio 122 at Posto 4 as a familiar meeting point for my clients. This helps you find your bearings, but your belongings remain your responsibility.
Footwear
You walk a lot in Rio. Bring a genuinely comfortable pair for the city and a simple pair for the beach. If you will hike, wear footwear with suitable grip; do not break in new trainers on the day of a long walk.
Rain and changing weather

A compact raincoat or small umbrella can be useful. On days of heavy rain, review your plans before going out: some trails, viewpoints and outdoor activities are no longer a good idea.
Insect repellent and sun protection
Sunscreen and insect repellent are two essentials. If you will spend many hours outside, remember to reapply sunscreen and drink water; Rio’s sun can be deceptive when it is windy.
Documents and copies
Bring the appropriate document for your trip and keep digital copies you can access even if you lose your phone. Do not keep your document, cards and all your cash in one place.
Money and cards
I would travel with at least two payment methods and keep them separate. Carry only the cash you expect to use that day and always check the amount on the screen before tapping or inserting your card.
Phone, battery and connectivity
Save maps, your accommodation address and important contacts. A power bank can be very useful on long days, especially if you use your phone for photos, maps, transport and payments.
Medication
Bring enough of your usual medication and keep prescriptions or documentation where required. If you use a specific medicine, do not rely on finding exactly the same brand when you arrive.
What I would leave out
Too many shoes, expensive jewellery, clothes that need special care and devices you probably will not use. Leaving some space also lets you return with purchases without making your suitcase a problem.
Hand luggage
Your travel document, medication, essential chargers, a basic change of clothes and anything you cannot easily replace should travel with you rather than depending entirely on checked luggage.
Before closing your suitcase
Check the forecast for your dates, the activities you will actually do and your type of accommodation. Someone coming for beaches and city life needs different luggage from someone hiking, attending events or visiting several destinations in Brazil.
My rule: if an item of clothing does not go with several others or serve a specific activity, it probably does not need to travel with you. Rio is much more enjoyable when you travel light.
I pack in layers and for different plans: light clothes, one extra layer for air-conditioned interiors, something for rain and shoes you can wear for hours. Separate swimwear and a bag for wet items; bring only the medicines you use, with their packaging or instructions. Keep a change of clothes in your carry-on in case checked luggage is delayed, and check weight limits before leaving.