The best way to save money is to grab a self-catering accommodation when you visit. Not only do you skip out on expensive restaurant meals, but you get a chance to truly travel like a local when you rub shoulders with them in places like markets and grocery stores.
Find yourself an apartment in Leblon, just a few blocks from Rio de Janeiro’s beaches, and you can get your groceries done at the nearby Hortifruiti. It’s a zig zagging store that starts off with produce at the front, bakery in the middle, and then meats and dairy waaaay in the back. You’ll find exotic fruits, huge avocados, and very inexpensive meat at Hortifruiti.
Here’s a video tour of what it looks like to do groceries in Rio de Janeiro.