Air popped popcorn is the easiest thing. We found an $8 microwaveable bowl that you can put dry kernels (and maybe a little olive oil) in and have a hearty snack that's under 100 calories a pop.

https://www.walmart.com/ip/Korcci-Microwave-Popcorn-Popper-BPA-Free-Silicone-Hot-Air-Microwavable-Popcorn-Maker-Bowl-Use-In-Microwave-Oven-Blue/424391615?wmlspartner=wlpa&selectedSellerId=10405