Nationals of countries outside of the European Economic Area require a Work & Residence Visa to work in Spain. Individuals can't apply for such visas; only employers can.
Your chances of finding an employer prepared to apply for a visa (for work in low-skilled employment) are almost nil. Nearly a quarter of all the Spanish workforce are unemployed. (In the youth sector the unemployment rate is around 50%). So it's extremely unlikely that any employer would consider going through the hassle of seeking a visa for an overseas worker when there are thousands of local people wanting a job. Further, it's even less likely that the Spanish immigration authorities would actually grant such a visa. (They're usually restricted to people who've got specific skills which can't be offered by Spaniards, such as world-class footballers and pioneering surgeons).