The meaning of having a dream about a thermos is varied as it depends highly of the actual circumstances in dream as well as the appearance of the thermos itself. In some case your mood during the whole dream has an importance also.
If in the dream you see a thermos that is empty but not damaged in any other way it means that one of your friends will ask you for a big favor in the near future. You might be quite hesitant to say ‘yes’ to their request as it will put you under risk to some degree.
A dream in which you will see a full thermos (regardless of the actual nature of the drink inside) can be interpreted as having a positive meaning for your earnings. It signifies that every bit of your effort will be decently rewarded in a monetary sense.
If you dream that you are filling an empty thermos with some drink it means that you will realize your mistake quite soon. Despite your conviction that you had made the right decision soon you will realize that things are not as shiny as you thought.
If you dream that you pour a drink out of thermos and into a cup it means that you will be more than happy to help one of your friends when the ask you for help. Alternatively, it can indicate that you have a rather caring and altruistic nature.
The meaning of a dream in which you would break a thermos by accident is that you will lose patience soon with one aspect of your professional life. You might realize that some arrangement in your professional life or career is taking up a bit too much of your time and energy. Alternatively, a dream like this one is a sign of conspiracy against you in your professional life.