This phrase doesn't exactly constitute slang, but rather a colloquial and idiomatic expression. It's a metaphorical well-wishing phrase from Cuba, very similar to 'May your cup always be full' in English. It essentially means 'May your life always be joyful and prosperous'. 'Guarapo' refers to a sweet drink made from sugar cane, and 'hielo' means ice, which symbolizes refreshment or comfort.
Examples
- Spanish: A pesar de nuestras diferencias, Dios quiera que tu guarapo siempre tenga hielo.
- English: Despite our differences, may your sweet drink always have ice, or in other words, may your life always be joyful and prosperous.