Option 1- Spot clean your bag with a little soap and water. Then rub and rinse with a cloth.

Option 2- If your mochila bag is due for an over all clean you can but your bag in the washing machine. It is best to put the bag in the washer on its own. Then turn washer on cold water and select either the delicates cycle or the shortest cycle.  Once this is finished you can hang dry your bag.  You then will have a perfectly clean and will be looking brand new.