What kind of strategic partnerships have you had with other stores? (Marketing)

My partner and I have been actively trying to market our shop (food & beverage cpg, one product) for the past few months and are at a standstill with not much success. We've done the classic fb/ig ads and didn't see anything notable while we ran ads ourselves and even after we brought on a digital marketing studio. Did the whole 'influencer' charade with horrible results. Then we spent a few weeks designing a direct mail campaign that also flopped.

Since then I've been trying to think of some unconventional routes to market the brand. Been reaching out to tons of subscription boxes – lots of which are super interested in having our product but can't afford/aren't willing to share our cost with us (we can't afford to give free product either). Now in a desperate measure I'm considering reaching out to other dtc kitchen/home/food ecommerce brands in a complimentary space and seeing if we can somehow partner and offer our product for sale on their website and we split the proceeds (our product is pretty universal and a great upsell item).

I'm wondering how to best approach other companies about that idea. Has anyone here done something similar, or some other kind of unconventional marketing?