So my japanese studies sort of slipped a bit because I decided to learn another skill. However, I don't want to lose all my hard work in japanese so I think it would be very stupid of me to not even do my anki reviews. My two anki decks are just all vocabulary and grammar. Any tips?

I had 600 RTK reviews that I hadn't touched in months to do after slipping up with studies. I just picked a times (it was vacation) and tried to whittle down the largest chunks I could. (At the time I wasnt feeling as motivated so I only did 200-300 card chunks). Factoring in all the failed cards (probably half of them got failed at least once), it took me between half a week to a week to get the reviews back down to acceptable levels. This is one of the few times I would say just do as many as you can, for as long as you can, and then take a break where you only do reviews and don't add any cards at all.

^assuming you want to keep up with the anki decks.

I'd say work by chunks of 100-150 cards and try not to spend more than 5-10 seconds by card.

I second the chunking suggestions. Otherwise, go hardcore for a few days. I was too busy to do reviews during the time before I left Japan, and so I had ~1,800 vocab/grammar cards piled up. I went through all of them on my flight back to California (I went at a rate of about ~200 cards per 10 min, while taking breaks in between every 2-3 10min blocks. It only took around 1.5-2 hours total).

In any case, going hardcore every now and then is great not only for your studies, but also your focus in general. When I was going through Core6k, I studied from the moment I woke up to the moment I went to bed 2 or 3 times. I made quick meals with little cleanup involved (breakfast: cereal, lunch: ramen, dinner: pizza). On each of those days I added, learned, and reviewed around 350-400 new words. The regular days seemed like nothing after the hardcore days. The focus and motivation I gained crossed over into other areas of my life as well.