There is salt in soy, so not a good idea.
You can only have what is in the book I'm afraid. Bean sprouts are a no.
Personally don't find SS+ particularly exciting! Still nice to look forward to a bit of chicken or fish though. I put mine in a micro bowl, add curry powder and black pepper, cover with clingfilm and nuke for 6 mins. Tastes lovely with a beautiful dry green salad lol