Replace single-use zip bags with a couple of reusable silicone bags or glass containers for freezing and packing snacks. Wash and reuse them for years.
A zip bag weighs about 5 g; two a week is roughly 500 g a year. Silicone is a silicon-oxygen polymer, not a carbon-chain plastic, and does not fragment into microplastics as readily.
The catch: silicone does not biodegrade and consumer recycling is effectively unavailable, so it only makes sense as a durability swap that displaces many single-use items. Glass containers are the fully recyclable option.