sack of dreams

Sack of dreams is the term for a relationship that is, simply, doomed to failure. This is often because the relationship is not serious, or just because the people are too young.
This might be the first girlfriend/boyfriend you had, as you likely were not ready (or legally able) to get quite so serious yet.
This term is particularly effective in the labeling of teens and their short-lived relationships. Make sure to tell your friends, but the Spanish is always better!
It's like a code:
Sacko de suenos de (Person X) y (Person Y).
It's pretty hard to understand unless they speak Spanish, and still, the phrase is obscure.
If you think that sack of dreams is random, it is completely up to you to choose how to diversify it and make it fit the needs of the relationship you are mocking. For example, making a dream-catcher and randomly handing it to Person X/Y, or decorating sacks with hearts and throwing them on the floor behind Person X and Person Y walking near each other or together.
Have fun with this!

Sacko de suenos definition by example:
Person X and Person Y are walking together.
You: "Sacko de suenos!" (sack of dreams)
Person X: "Huh?"
You: "Oh, it's nothing."
Devious chuckle...
(Please only do this with understanding Persons X and Y, or you might get rumors spread about you or simply be named Juan until next year).
Sacko de suenos has been used, as you are referencing the relationship between Person X and Person Y.