Answer: desayunemos
Explanation: You must use the subjunctive form of the verb in Spanish when saying something like "es aconsejable que" (= it is advised that). The indicative present forms of the verb desayunar include desayuno, desayunas, and desayunan; however, desayunemos is not one of them because it is subjunctive (the indicative form would be desayunamos).