Once the can or bag open, we often wonder what to do: drain? rinse? keep the can juice?
Often, the can only contains water and a bit of salt in addition to the vegetable. But it can also be a cooking juice with spices or natural aromas which was specifically prepared to enjoy with the vegetables in it. Up to your taste to decide whether to keep those juices or not. A nut of butter to garnish carrots and peas, a drizzle of olive oil in green beans heated on the pan: up to you to add what you love to make them taste better!
Only exception: legumes (white or red beans, lentils or chickpeas) which you better rinse. This way, you avoid the bloated feeling which they can cause.
For ready-to-use, it is all in the name: it is truly ready to be eaten. It does not contain any conservatives, it was already washed, rinsed and drained. It would be silly to do it all over again!