A “treulose Tomate” is a German humorous expression/term for a faithless and not reliable friend/person (literally translated: faithless tomato).
Yes! This sticker is the right present for a fair-weathered friend – of course, the piece was created with full intention as a very raw and messy thing, but it should just serve right to be a fair punishment for the donee - put the sticker on his/her back, car, door, whatever.
A humorous reminder to be a more faithful compadre and to appreciate and care for a friendship more.
Of course, if a treulose Tomate got enough self-awareness he or she can wear a piece of this design as a peace offering.
The German sentence "Kekse essen DADA und da" makes no-sense or sense in the tradition of dadaism. You can roughly translate it into "Cookies eat DADA and there", but in German a Keks (plural Kekse) can also take on other meanings like head, nerves etc. depending on the saying or context it is used.