What can you use for homemade flux?

Could you elaborate on potential alternatives for homemade flux? I'm particularly interested in knowing if there are any common household items that could be utilized for this purpose. I understand that flux is typically used in soldering applications to clean metal surfaces and aid in the bonding process, but I'm wondering if there are any innovative substitutes that could be safely and effectively used at home. Could you provide a few examples and perhaps discuss the safety considerations associated with these alternatives?