Should I form a non-profit, llc, s corp.? etc.?

I am one person who is looking to sell environmentally friendly products. I was thinking of donating a portion (maybe 20% of proceeds) to environmental causes. Should I incorporate as an L.L.C? Or form a non-profit? Or just be a sole proprietorship? I am most concerned about getting taxed the least. Why would a company like Newman's Own donate 100% of profits to charity, instead of just forming an non-profit?