Cans raise your consumable limit, and collecting them all gives a suit. Every can is missable past the points of no return, so check each area before you leave.
Cans by area (49 total)
Eidos 7: 3
Xion: 8
Wasteland: 15
Matrix 11: 3
Great Desert: 16
Spire 4: 4
Rewards
Rewards at 7 and 14 cans, from the special vending machine in the Xion safehouse.
All 49: the Black Pearl suit and the Can Collector trophy (silver).