To add to that a bit, adding water to your high-percentage isopropyl alcohol will just turn it into low-percentage isopropyl alcohol, likely with trace contaminants if you are using something other than distilled water. So, you should use distilled water if you are going to dilute it. That's what the remaining percentage is made up of to begin with. A 50/50 mix with high-percentage isopropyl alcohol like that would just result in you having 50% isopropyl alcohol, for example. You should be able to pick up a gallon of distilled water for about a dollar.
Often, you can get away with completely submerging electronics in isopropyl alcohol, or a mixture of isopropyl alcohol and distilled water. The more alcohol that's used, the easier it will clean and the faster evaporation can occur, but you are also likely to end up with more poisonous and flammable vapors in the air. It can also potentially cause skin irritation and be absorbed through the skin, so you might want to wear gloves when washing things with relatively large amounts of it. In the case of a keyboard, alcohol might also remove lubricants within the key switches though, so be aware of that.
I did a quick search and found a video of someone cleaning their keyboard in this manner, and by chance it actually happened to be a K70 with a soft-drink spilled on it...
View: https://www.youtube.com/watch?v=nPhXt_wmLkU
In their case, it looks like they used a very dilute mixture of 1.5 liters distilled water to 0.1 liters 99% isopropyl alcohol, which would make for a less than 7% mixture. I would probably use a much higher percentage than that, but again, you would want to make sure you did so in a well-ventilated area like outside, and would probably want to wear gloves. You'll also notice that they actually repeatedly press the keys while submerged to make sure they are getting the alcohol inside them and the contaminants flushed out.
It looks like they used a blower fan and possibly a heater to dry them out for some hours after removing them from the mixture, though something like a hair dryer and just air-drying may work well too. Excessive heat might potentially warp the plastic though. I would shake out and press the key switches to remove excess water first. It's probably worth leaving it out a couple days afterward to make sure everything is thoroughly dry before testing it.
In this Paul's Hardware video, he recommends using full submersion as a last resort for a keyboard, and outlines some other methods of cleaning out the key switches that target just the switches in question, so that might be worth trying first...
View: https://www.youtube.com/watch?v=Tw_tpElJbxY
If you do decide to fully submerse the keyboard in a distilled water alcohol mixture, or otherwise clean the internals more thoroughly, here's another video outlining the basic process for opening up the K70, since there are a couple hidden screws and some other things to note...
View: https://www.youtube.com/watch?v=ZeIqMQ2WDaY