If you have no refrigeration, how long is canned food good for after you open it, since it was sterile until opened?

A few hours: Once you have opened up a container and touched the inside, even with a spoon, the contents are then contaminated with bacteria. Depending on the conditions, toxins can be elicited within even a few hours. Certainly this answer is affected by how extreme the environmental conditions are and what the actual contents are, but if possible it is best to err on the side of safety. Good luck.

Canned food: A stored canned food supply is an essential emergency preparedness measure. Once opened, canned food is then perishable because it has been exposed to the air. After two hours without refrigeration at anywhere from 4-60 degrees Celsius, it should be discarded. Inspecting the food is good but one cannot detect dangerous contamination.