No milk. Use fil (sour milk), yoghurt or something similar. Put cereal on top, no mixing. The cereal touching the "liquid" get soggy while the rest stays crisp giving the best texture heterogeneity. Berries are awesome, frozen a super convenient alternative. If using frozen mix these with dairy before adding cereal.
Your fermented dairy of choice brings a nice crispy and fresh acidity to the meal. And if it (still) have an active bacterial culture it is super good for your gut.
Jam, agave, or maple syrup should be good with muesli & yoghurt to my taste. Light molasses may work in moderation, and I've heard good things about sorghum syrup.
Are you from Sweden btw? Filmjölk/Fil I learned today has no English term. I am from the Netherlands and my mom used to get us Viili all the time, that is where my memories connected with you mentioning Fil. We also had Kefir but Viili was my fav, better than yoghurt. It's hard to get here nowadays.
Thanks for mentioning, I looked Kama up and it is certainly a breakfast unknown here but the recipes I looked up read delicious. Sorta fine grained roasted muesli. Fiber and protein on steroids. Also I learned versions of this is eaten Sweden, Finland, Russia and even Turkey. Also seems much healthier than any 'western' factory cereal as the recipes I have seen only require salt.
That is my preferred breakfast. I prepare it the night before in a glass to allow the bottom layer tons of time to soften like you say but then I mix it all just before eating. I tend to use kefir since if I want fil I've gotta make it myself but as you say anything similar gets the job done.