It was a trip to 3 places: Lunch, Guamantong Cave, and Kinabatangan River
The driver basically doubled as our tour guide. He was very friendly and tried to make us as comfortable as he possibly can. He was also very laid back. However, he doesn't really explain anything and only had basic knowledge of the animals/places. He drove us around in an old taxi, which would have been fine except that the journey to the cave and river was long and the roads were developing/under construction. The long drive back to our accommodation was particularly uncomfortable.
We had lunch in a local halal Chinese shop. It was noted that our tour guide wanted us to feel comfortable and there weren't a lot of restaurants along the way. For context, we are local Chinese from KL. The food tasted good but I didn't like that he didn't really bother ordering for us. The food is quite different from the food in KL. The waitress who took our order just told us what people normally ordered and we just ordered that. The food was individual (rice or noodle) dishes. They were also cheap.
Guamantong Cave was pretty much just a bat cave with birds and cockroaches. Be ready for a lot of guano (bat excrement) and cockroaches. Our tour guide gave us face masks to help with the smell - but it really isn't that bad once you get used to it. Standing in front of a full dumpster is worse. Bring your best torchlight, the ones where the light can hit far away. Your phone lights won't do much except shine at guanos and cockroaches around you. Also, the walkway and railings were covered with guanos and cockroaces. If you are the type that feels icky cause of roaches, I suggest covering up a bit just to feel pseudo-"safe". Water drops down from the cave sometimes but because of the environment, you tend to question it. When we went, there were workers picking out birds' nests. It was quite something, watching them just chatting away and climbing up the cave in wooden ladders and ropes nonchalantly. Overall, while it was interesting, the visit was quite short (the cave wasn't very big). I felt like we could have just went there ourselves with a good car/four wheeler (cause of the roads). Because of the timing of the tour, we visited the cave early in the afternoon - in which, nothing was really happening. Apparently, if you visit the cave as the sun sets, you can see the bats leave the cave.
Kinabatangan River is just a massive river surrounded by jungle. The jungles look like they're mangrove swamps but I can't tell for sure. The boat ride was nice and scenic. The boat wasn't small and we weren't splashed by water the entire way. It also wasn't raining when we went but we were prepared with raincoats. If you have binoculars, bring them. We saw lots of monkeys (including the proboscis monkey) and birds (including the horn bill). Monkeys were easy to spot and seem fairly common. Orang utans, however, prefer to be deep in the jungle. Spotting the birds are harder seem to depend on luck. Apparently, you can also sometimes spot crocodiles but we were not lucky enough to have that happen in our trip. Our tour guide and the skipper/"boat driver" were very nice people and took their time to try showing us as many wildlife as they could. In the end, we were back at our accommodation at about 9-10pm.
Overall, I personally felt like the tour was alright but not worth the money.