Hyacinths are quite top heavy. I plant them close together (but not too close) so they can support each other. Garden stores also have plant supports that work well.

I read that the famous gardens where the beautiful photos come from, Keukenhof, use wires to keep those beautiful heavy heads in their photos straight up. They just run a wire down the stem into the bulb.

Florists often just put a bamboo stick down in the pot and attach the flower stem with a bit of florist's tape. A bit of droop keeps them from looking stiff and unnatural.

My experience with growing hyacinths in the garden is that second year flowers are not as full and heavy and stand up nicely.