Adult tephritid fruit fly females require protein sources for adequate egg production, and ammonia and its derivatives serve as volatile cues to locate protein-rich food. The attractiveness of beer waste and the commercially available baits Nu-Lure^® Insect Bait, Buminal^®, and Bugs for Bugs^® Fruit Fly Bait with and without ammonium acetate or ammonium carbonate to males and females of Bactrocera dorsalis (Hendel) and B. cucurbitae (Coquillett) (Diptera: Tephritidae) was quantified in semi-field cage studies in Hawaii. Evaluations also compared the relative attractiveness of the baits to that of the standard bait GF-120^® NF Naturalyte^® Fruit Fly Bait. Our findings indicate that ammonium carbonate did not exert any effect on the response of B. cucurbitae or B. dorsalis to the protein baits evaluated and that the addition of ammonium acetate to beer waste and to the commercially available bait Bugs for Bugs^® can improve bait attractiveness in particular to females of B. cucurbitae. Beer waste laced with ammonium acetate performed as well as the standard fruit fly bait GF-120^®. There were variations in the level and type of response between B. cucurbitae and B. dorsalis, and such variability was dependent upon the type of bait being evaluated. For example, there were several instances where baits lacking ammonium acetate (e.g., beer waste and Nu-Lure^® for B. cucurbitae; Buminal^® for B. dorsalis) were as attractive as GF-120^®. Results are discussed in light of potential applications associated with the use of beer waste as a low-cost, readily available material for fruit fly monitoring and suppression.