Can STDs be transmitted through urine?

Urine and STDs. Nope. Not at all. Urine is sterile and there can not be any disease transmission.
NO. No, transmission of HIV through urine has never been established and is not a risk. Unless, there is significant amount of blood in the urine and you have significant exposure to the bloody urine for a period of time. Other stds are also highly unlikely to be spread by urine and cannot be spread by toilet seats or other surfaces of fomites or surfaces.