We present wireless inductor-capacitor (LC) tank sensors constructed by the three-dimensional (3D) additive manufacturing technique. Fabricated 3D structures with hollow channels are filled with liquid metal (silver particles) to form basic electrical components including inductors and capacitors. In the prototype design, a radio-frequency (RF) LC tank with resonance frequency at 0.53 GHz is realized. This LC tank sensor is utilized in rapid detection of liquid food (e.g., milk and juice). Specifically, the resonant frequency of the LC tank changes as the dielectric constant of the liquid food deteriorates over time and the signals are detected via an inductively coupled reader wirelessly. In the preliminary tests, a 4.3% frequency shift for milk stored at room temperature after 36 hours was obtained. This work presents a new class of manufacturing concepts to construct arbitrary 3D electrical systems for wireless sensing applications.