In order to preserve evidence, crime labs recommend that those who've experienced sexual assault avoid showering, washing, peeing, changing clothes, and even eating, drinking or brushing their teeth before the SART exam. That said, not doing these things is not wrong and doesn't mean the survivor has made a mistake.
Now, yes, it is great for people to go to the hospital or medical facility to receive this type of support. But a lot of people choose not to do this. Do not try to push anyone into doing anything that they do not want to do. You can offer them the information that you have learned and support them. But never try to push your wants and needs on a survivor.
Because the focus of the SART exam is to collect any evidence of the assault, while doing the SART exam, your friend may have to recount their assault. This may be really hard for them to do. In some instances, there may be a rape crisis counselor there to support your friend because they are trained to handle crisis situations.
Remember that if your friend wants you to attend a SART exam, be honest. If you cannot handle going and doing that role, don't go. It may be more harmful for both of you.
If you are supporting a friend who is getting a SART exam, remember that what has just happened to them was a lot, and that they may not be emotionally, physically and/or spiritually present. Be sure to check in with them and ask them what they need. Remember that you are with them because they trust you. So just be there, hold space for them, and ask how you can help.