It's there for emphasis.
'An toil leat biadh spíosrach?' would still mean 'do you like spicey food?'
As my old Gaeilge teacher would say it turns this sentence from a green apple into a nice juicy red apple!
Please correct me if I'm wrong mods, but wouldn't 'an toil leatsa biadh spíosrach?' give the same emphatic meaning that 'fhèin' would?