Is there a DIY product I can make myself to waterproof suede boots? I don't mean buying a can of spray.
Suede is a very difficult material to clean and waterproof as most products will damage it and usually beyond "restoring" to the original look.
Sorry, but If your boots are new or in good condition then I would say it would be better to pay for a product that is recommended for suede.
I know you said "don't mean buying a can of spray" but I have not found any reference to it being safe to use any "household" product on suede.
Maybe someone else will have a recommendation for a safe DIY with other than a commercial product but I would be very careful, or at least, be prepared if the result is not the way you wanted it.
This is what I have used and it does an excellent job but there are several products available that are recommended for suede.
I had a suede jacket back in the 80s as a gift and I kept it looking nice for years just by brushing it with a suede brush (it came with the jacket). There is no safe way to water proof it...except not to get it wet.
Enjoy your boots!!
You could use beeswax for leather, but I haven't found anything homemade that works for suede.