It isn't a DIY but Petco bendable bridges are and most likely always will be a definite favorite of mine
They're large enough for Syrians,reasonably priced(especially compared to other large bendable bridges at $10+ for a single bridge while the Petco ones range from $2-$4 depending on when you get them and if you order them online or buy them in store).
For a bit of a DIY project that is very simple to do daily and can be made in any size you want,strips of toilet paper in a pile with healthy treats or the main diet hidden inside have gone down really well in my experience.
I'd recommend a DIY platform(hamster-safe untreated wood with wooden dowels,use Elmer's glue to attach the dowels and depending on the platform's purpose a popsicle stick edge may be necessary).These can be made to whatever size you want,and are especially good to hold a sand bath or water bowl(highly recommended over bottles in most cases,as hamsters drink a lot better from them and the water will be fresh if you're refilling the bowl often enough).I personally use reptile water dishes as they work perfectly for hamster water bowls if they're shallow enough and not too large,for example Petco carries a $3 bowl that is excellent for this purpose.Just make sure there are no weird holes or places for a hamster to get injured,as with any other item in the cage!
https://www.petco.com/shop/en/petcos...l-reptile-dish