Opened formula milk

My 2 months old had milk allergy and is only able to drink extensively hydrolysed milk. I’ve bought 3 large cans all of differently Brands (Friso, similac soy, similac regular) to let him try before finally settling on Aptamil Allerpro. The cans were opened for about 2 weeks and are all still 90% full. What should I do with them other than throw them away? Trying to minimise waste. I don’t mind giving them away but is it safe?