Can I heat up overnight oats

Soaking oats in milk overnight makes for very good porridge, with little effort in the morning as you just have to heat it through. So you're very close to something standard.

The golden syrup and fruit won't come to any harm from being soaked then heated, though you could equally stir them, or just the fruit, in at the end.

The only thing needing a bit of care is the yoghurt. It's probably better to start with it mixed in rather than stir it into hot porridge, as adding yoghurt to hot food causes it to separate, as does overheating it. So assuming you put your entire soaked breakfast into the microwave, you should heat it fairly gently, perhaps 1 minute on high, stir, 30 seconds on high, stir and see if it's hot enough (with further 30s bursts until it is). If your microwave is very powerful or uneven, the first step will need to be shorter. You may find with testing that you can just blast it until it's hot; this partly depends how much yoghurt there is in relation to the amount of milk.

I think heating overnight oats would not be a great idea because the texture of the oats change when it is left overnight with milk/yogurt and is not suitable for heating. I follow a standard oats recipe every morning where I mix the oats with just enough water/milk to cover it fully in a bowl and throw it in the Microwave for exactly 2m 30s. It turns into a very nice porridge which I then mix with fruits like banana and strawberry and add walnuts and raisins. For optimizing purposes, my walnuts and raisins are stored in the same box and I just take a handful out each morning. I cut the fruit fresh every morning but that's like 2 mins of work max. I totally understand how mornings are hard and optimizing each minute is the key. But my oats routine only takes like max 5 mins and is a delicious and healthy way to start my day.