Biodegradable stickers out of sugarcane?
Artist Harmony Hardin has curated an excellent resource for those who want to create promotional materials that are environmentally friendly.
In her Youtube video, she discusses whether stickers can be bio-friendly and includes in the program notes an extensive list of sources for environmentally sound stickers, packaging, and papers.
None of those are Print On Demand products, so there’s a minimum order. The services also have compostable mailers and other environmental packaging materials that look fun.