Here is the chemical equation for the reaction between fish sauce and vinegar:
$$C_6H_{12}N_2O_2 + CH_3COOH → CH_3COOC_2H_5 + NH_3 + H_2O$$
In this equation, C6H12N2O2 represents the amino acids in the fish sauce, CH3COOH represents the acetic acid in the vinegar, CH3COOC2H5 represents the ethyl acetate that is produced, NH3 represents the ammonia that is produced, and H2O represents the water that is produced.