混饭 is colloquial and self-deprecating - implies you're getting by without any grand ambition. The fuller idiom 混饭吃 (literally 'mix rice to eat') and 混口饭吃 ('mix a mouthful of rice to eat') are more common in conversation. Avoid in formal/job-interview contexts.
memory
混 here doesn't mean 'mix' - it means 'drift along, muddle through'. Same 混 in 混日子 ('drift through the days'). Combined with 饭 ('rice/food'), the literal image is 'just chasing the next meal'.
