This study was conducted on the energy-absorbing characteristics of periodic two-dimensional square honeycomb sandwich structures, which were made from short sugar palm, kenaf, and pineapple leaf fibres (PALFs) reinforced with polylactic acid (PLA). Short fibres were mixed with PLA in a batch mixer at 180°C, with 20 wt% of fibre mass and 80 wt% of PLA pellets. The biodegradable sugar palm/PLA composite sheets underwent the hot compression process and were cut into single and double-slot square honeycomb panels. The slotting method was used to assemble the periodic two-dimensional square honeycomb sandwich structures. The biodegradable sugar palm/PLA composite and honeycomb sandwich structures underwent tensile and quasi-static compression tests. Finite element modelling was used to simulate the damage behaviour, which incorporates biodegradable composite properties and geometric imperfections. The results indicated a small decrement in tensile strength for the recycled sugar palm/PLA composite. It revealed that the double-slot design of the pineapple/PLA sandwich structure significantly increased by 1.33 times compared to the sugar palm/PLA sandwich structure. Moreover, it notably reduced the compressive strength of pineapple/PLA (66.4%) and sugar palm/PLA (31.5%) composite sandwich structure. Finite element modelling showed good agreement with experimental data, which had a 7.11% error in energy absorption parameters. It was concluded that these biodegradable composites have potential for specific energy-absorbing structures.